• Table of Contents
• A first in Japan | [Underwater National Park Designated] A rare environment
• Guide to this article | Introduction to people living in the area
• The overwhelming amount of fish that the sea boasts. | Characteristics of the sea in Ainan Town, Ehime
• Underwater scenery trip | Special protected area of the national park [Yokoshima]
• More Articles and Outside Resources ｜Southern tip of Ehime, Ainan Town, Nishikai Sightseeing Boat

A first in Japan | [Underwater National Park Designated] A rare environment

Ainan Town's underwater scenery is diverse, with environments teeming with colorful corals and fish, and rugged cliffs. The sea around Ainan Town is characterized by the fact that it is an environment where fish of all sizes can live, and that many of these exist in a small area. In short, the environmental conditions under the sea are diverse, and the town maintains a very rich sea.

Just a slight change in location can cause a drastic change in the types of living organisms (in this case, corals). The differences are so clear that you can instantly tell just by looking at them that the environment has changed. Japanese marine biology researchers say it's rare for the environment to change so much in the same ocean.

It's a shame we can't introduce everything here, but the ocean is rugged and has many different environments, including sandy areas, steep slopes, rocky areas, small rocks and sand, mud, and cliffs. The density of these areas creates an environment where a variety of fish can live. Due to the richness of the ocean, underwater scenery, and abundance of underwater resources, it became Japan's first "underwater" national park to be designated a protected area in 1970, and since then it has come to be affectionately known as an "underwater park," and has become famous throughout Japan, having been visited by Emperor Showa, among other things.

*As of 2025, the law has been revised and the name has been changed from "underwater park" to "marine area park."

Guide to this article | Introduction to people living in the area

Nice to meet you, my name is Takahashi and I am a guide instructor. As of 2026, I am managing and operating the Nishikai Tourist Boat Facility in Ainan Town. I usually work as a tour boat driver and diving instructor, but I also use the videos and images I take underwater to show people around the ocean, both on land and at sea.

I originally lived in Tokyo for over 30 years, but when I was in my 30s, I visited Ainan for the first time and tried diving for the first time, which led me to decide to stay and live in Ainan. It has been over 10 years since I came to Ainan, and now I have obtained an instructor trainer qualification from SSI (Scuba Schools International), and I teach everything from beginner courses to instructor training.

Recently, I have been focusing on giving lessons about the ocean to children, and I aim to be a guide who can help them gain a deeper understanding of the ocean.

By the way, for those of you wondering, where is Ainan Town?
It's in Ainan Town, south of Ehime.

Access to Ainan Town, Ehime -【Google Map】

The overwhelming amount of fish that the sea boasts. | Characteristics of the sea in Ainan Town, Ehime

Not only are there many types, but there are also many quantities. The overwhelming amount of fish is so great that it forms a wall when observed underwater. The fish in the photo are a school of grunts. These fish have the habit of following in unison when the leading fish changes direction. The loud "bang" that can be heard when thousands of fish change direction is also impressive. The scene in the photo shows the moment when they all descend from shallow water to deep water at the same time.

One thing I recommend is "fish observation from the pier." One of the characteristics of Ainan Town is that you can observe fish even from land while walking. This photo shows a school of fish gathering under a boat moored at the pier, but in some places, you can also observe hundreds of horse mackerel and schools of amberjack preying on them, right next to the pier.

Small fish are also a prerequisite for the habitation of larger fish that eat them. Nearby, there is a fish called the golden-spotted lionfish hiding in the crevices of the coral colonies, and a lionfish, which is famous for its poison. It takes aim and, when the right moment comes, swallows the fish in one gulp. It preys with such speed that it is difficult to catch with the naked eye. The food chain is occurring in the ocean, even in places close to us.

Underwater scenery trip | Special protected area of the national park [Yokoshima]

Finally, I would like to introduce the underwater scenery of Yokoshima, a special protected area. A distinctive feature of this area is the coexistence of hard corals and soft corals. The two types of corals have different environments, so they rarely coexist. Ainan Town has a sea that is hospitable to living creatures, allowing these two types of corals to coexist.

A little bit of trivia: Corals form skeletons. Hard corals are covered entirely in skeletons, but soft corals are soft because they only form bone fragments called "spicules" within their muscles. If they didn't have bones, they would be called "sea anemones." Did you know that if they floated in the water, they would be called "jellyfish"? Corals, jellyfish, and sea anemones actually have almost the same body structure.

Fish gather in ridge-like areas along with the coral colonies. Fish that eat coral or use it as a hiding place gather around, along with predatory fish, creating a rich ecosystem. This scenery stretches for over 2.5 km on Yokoshima Island, which is a national park.

The stingray is another distinctive fish. It uses its narrow mouth to target crevices in coral and prey on other fish.

There are many different types of landforms, and natural caves are also great photo spots.

More Articles and Outside Resources ｜Southern tip of Ehime, Ainan Town, Nishikai Sightseeing Boat

▽Ehime National Park Nishikai Sightseeing Cruise [1/4] | Shop Introduction

| Ainan Town's Marine Environment

This is the article on this page.

▽Ehime National Park Nishikai Sightseeing Cruise, official website here (Japanese, external site)
https://nishiumi.info/

• Table of Contents
• Beach clean-up activities spanning generations for over 30 years
• Underwater conservation in national parks | Coral conservation activities
• Effective utilization of fishing villages and town conservation marine industry "UMIGYO"
• More Articles and Outside Resources ｜Southern tip of Ehime, Ainan Town, Nishikai Sightseeing Boat

Beach clean-up activities spanning generations for over 30 years

Many people gather at the parking lot of the Saikai Tourist Boat

With the slogan "Give back a little to the ocean of our hometown," participants take a break from their everyday lives and think a little about the ocean while picking up trash. This beach clean-up activity will mark its 31st year in 2025.

Coral colonies have been growing in the sea off Ehime for decades. In fact, it has only been discovered recently that many corals over 300 years old have been discovered. The rich seas have remained since the time when samurai lived there during the Edo period 300 years ago. In recent years, they have become famous among marine researchers.

Perhaps because the name of Ainan Town is gradually becoming known, more and more people from outside the town are participating in our activities.

This activity was originally started by an old man who has been diving in these waters for over 40 years. In 2025, he will be 74 years old, but he is still active as a guide instructor. The people who have been helping us since then are still supporting our activities, and recently new people have joined us, and the number of participants has increased.

More than 50 people participated in the 2025 activity. This activity is held every year in the last week of June, and anyone who has obtained a C-card can participate.

Our activities began to be recognized widely, and in 2025 we received an award from Ehime Bank. Standing on the right is my grandfather, a 74-year-old active guide instructor. On the left is me.

Underwater conservation in national parks | Coral conservation activities

In 2025, the guide instructor, who will be 74 years old, established the "Ainan Coral Protection Council" shortly after starting the beach cleanup. He gathered local volunteers and created an organization to carry out coral conservation activities. Activities will begin in the winter when the high water temperatures have ended.

Line transect method: A 100m line is drawn on the seabed, and the bottom sediment is examined every 50cm to check the degree of coral coverage. Spot check method: An observer swims for 15 minutes and visually checks the degree of coral coverage, size, and species preference.

We have been observing these at 10 locations every year for over 10 years, and have been keeping a record of the data.

The coral community in Ainan Town has been gradually increasing since around 2014. Although the coral was damaged once in 2018 by a large typhoon, it has now recovered and new coral babies can be observed every year.

Located at the southern tip of Ehime Prefecture, Ainan Town continues to enjoy abundant nature, living up to its name as a special protected area of the national park, but it also faces other major problems. As the population declines, it is becoming more difficult to pass on the skills, culture, and history that have been developed up until now. I, Takahashi, am 44 years old, and there is a huge gap in the generation above me. I feel that the lack of succession of skills, culture, and history is a major problem even within Japan.

Another big goal for the future is to pass it on to the next generation.
This is where the marine industry "UMIGYO" comes in, which will be discussed later.

Effective utilization of fishing villages and town conservation marine industry "UMIGYO"

"UMIGYO" is the name of an initiative promoted by the Fisheries Agency to revitalize fishing villages. It was formulated in 2022, and in 2023 Ainan Town was certified as a "UMIGYO" promotion model district.

Ainan Town was chosen as a model district for promoting the effective use of fishing villages because it has a thriving fishing industry and a rich ocean, including a national park. This became a major driving force for Ainan Town, where population decline is a major issue, to create a town of the future.

Maritime "UMIGYO" Local Government Initiatives

Many meetings were held to discuss how Ainan Town could continue to exist, with people from various industries, including fishing, aquaculture, tourism, food and beverage, accommodation, universities, government ministries, and banks, coming together and led by the residents rather than the town office. Many different things were discussed at the "UMIGYO" meetings.

Among these, "education" became an important theme that different businesses could agree on. Combining education and tourism to welcome visitors from outside the town as a whole is likely to become an important goal for the future.

Personally, I have begun to focus on "welcoming people from outside through wide-area collaboration" while utilizing the abundant ocean in the national park. This is the GreenFins initiative, which I will introduce later.

National Geographic

Before introducing GreenFins, let me tell you something. As part of the maritime industry "UMIGYO" initiative, Ainan Town was featured in National Geographic.
▽National Geographic website (external link)
https://special.nikkeibp.co.jp/atclh/TS/25/ainan_umidas0826/

They are trying to revitalize the fishing village that is on the verge of disappearing and bring back the town's vitality. The entire process has been covered and published as a single story. Coinciding with the 30th anniversary of National Geographic, Ainan Town is being introduced with the main theme of "the sea" and a focus on the people working in the background.

Green Fins

It has been decided that "GreenFins" will be introduced in 2025 as part of a wide-area collaboration. GreenFins is an international certification that sets out model rules for conducting economic activities while protecting the environment, focusing on diving and snorkeling. There are many things that we normally do, such as avoiding contact with living creatures and not scattering harmful substances, but we also thought it would be good to establish rules on a wide scale, such as avoiding anchoring as much as possible, so we introduced it to this region. This is part of the marine industry "UMIGYO" and is one of the projects I am working on.

The good thing about GreenFins is that it is a system that cannot be acquired by a single business. Acquisition is only permitted if the local government also participates. We believe that it is meaningful not to simply acquire qualifications or certifications on an individual basis, but to aim for acquisition as a region as a whole, including the local government.

It's important not only to protect the ocean, but also to let local people know how amazing and precious Ainan Town's ocean is. By continuing various activities, such as our regular conservation activities and the introduction of Green Fins, we were able to create opportunities for Ainan Town residents to dive in the local ocean. Everyone, including the locals, thinks they know about the ocean, but surprisingly, they don't. We are starting town development by letting people know about the preciousness of Ainan Town's ocean, which has been designated a special protected area in the national park.

Everyone at the town hall who obtained a C card

More Articles and Outside Resources ｜Southern tip of Ehime, Ainan Town, Nishikai Sightseeing Boat

▽Ehime National Park Nishikai Sightseeing Cruise [1/4] | Shop Introduction

▽Ehime National Park Nishikai Sightseeing Cruise, official website here (Japanese, external site)
https://nishiumi.info/

• Table of Contents
• Ainan Town, a town surrounded by ria coastlines | Many diving spots
• Simple introduction to underwater scenery
• Diving Style | Schedule & Facilities Introduction Saikai Sightseeing Cruise
• Recommended season, seasonal winds and water temperature
• Nearby hotel | About 10 minutes by car to the shop
• More Articles and Outside Resources ｜Southern tip of Ehime, Ainan Town, Nishikai Sightseeing Boat

Ainan Town, a town surrounded by ria coastlines | Many diving spots

Ainan Town, located at the southern tip of Ehime, is surrounded by a unique coastline created by a ria coastline. Due to the presence of uninhabited islands nearby, different environments are scattered across a small area. There are over 30 diving spots. A multi-day diving plan is recommended. The best time to visit is between July and the end of October.

Simple introduction to underwater scenery

Yokoshima, where soft and hard corals gather

Yokoshima, designated as a special protected area of the national park, has five diving spots. The three spots we often take people to are Yokoshima No. 2 Site, Yokoshima Fault, and Koyokoshima. Each spot has its own characteristics, so we will introduce the underwater conditions.

Yokoshima Site No. 2

Yokoshima No. 2 is a point where a ridge stretches out with a difference in elevation. The bottom at the tip is 35m deep, and the top of the ridge is about 10m. This is a terrain that attracts fish, so if you're lucky you might be surrounded by schools of grunts, silver-ringed herring, and amberjack.

Yokoshima Site No. 2

What all the points on Yokoshima have in common is the presence of colonies of hard and soft corals in shallow waters.

Yokoshima Fault

The Yokoshima Fault is a very shallow area, with a maximum depth of 14m and an average depth of 8m. A single rock stretches from north to south, but above it is a magnificent, unbroken colony of coral.

Koyokoshima Island

Like the other spots we've introduced so far, coral colonies grow in the shallow areas of Koyokojima, but if you go down to the sandy area below, you'll often come across large schools of fish. Sometimes schools of thousands of grunts and other fish will fall from above all at once, making this a spot where you can target both coral and migratory fish.

After the safety stop, we explore the cave before returning to the boat. It is a fun spot where the environment changes constantly during the dive, with corals, fish, and topography.

Diving Style | Schedule & Facilities Introduction Saikai Sightseeing Cruise

schedule

We dive three times a day.

8:30 meet up
9:00 Departure
9:30-10:30 1st dive
10:30(you can choose this time, when you wanna only 2dive/day)
11:00 Departure
11:30-12:30 2nd dive
12:50-13:30 Lunch Bento
13:45 Departure

2Dive 14,000 Yen
3Dive 18,000 Yen
Full rental 5000Yen + Divecomputer 1500Yen

Locations, Facilities, and Ships

Name of the shop: Nishikai Sightseeing Boat Address: 1599 Funakoshi, Ainan-cho, Minamiuwa-gun, Ehime Prefecture, 798-4205
Google Maps is here▽
https://maps.app.goo.gl/wuLyy78Vxgab5AWy9
Official website/Fun Diving is here▽ (Japanese)
https://nishiumi.info/scuba-diving-fun.php

The parking lot is large and can accommodate 150 cars, with a view of the ocean.
Please come to the reception desk in the building in the photo and tell them you want to go diving before the meeting time. We will guide you there.

Diving Style | Boat & Anchoring

We occasionally do drift diving, but the basics are boat and anchoring diving. We have created many courses with varying terrain, and we guide everyone on circular courses.

We also have SSI (Scuba Schools International) instructor trainers on staff, so we have the advantage of being able to hold all courses, including professional rank instructor courses. We will guide everyone with safety as our number one priority.

▽ Reservations can be made here: Saikai Sightseeing Cruise Official Website (external site, Japanese)
https://nishiumi.info/scuba-diving-fun-reservation.html
▽Seikai Tourist Boat Official Website Fun Diving Explanation (external site, Japanese)
https://nishiumi.info/scuba-diving-fun.php

Recommended season, seasonal winds and water temperature

Recommended time: Mid-June to late October

In the summer, the sea is as calm as a lake, as shown in the photo above. We recommend visiting from mid-June to the end of October.

You can dive in winter, but the seasonal winds are often strong from November to the end of May, so the seas tend to be rough (January and February are the peak months). When the sea conditions are bad, we often cannot go to Yokoshima, which is our main diving point.

Ho

During the winter, there are often 6-7 stormy days out of every 10 days.

*A detailed wind forecast will be announced two days before your reservation. Based on that forecast, we will contact you if there are any problems with the sea conditions.

Water temperature: 16°C to 28°C (minimum water temperature is in February, maximum water temperature is at the end of August)

The maximum water temperature in this area is 28°C. The water is warmest from the end of August to early September. From mid-June to the end of October, you can comfortably dive in a 5m wetsuit. (On October 22, 2025, the water temperature was 26°C.)

The lowest water temperature is 16°C around February. As the outside temperature also drops at the same time, we recommend wearing a dry suit from November to the end of May. Dry suits are limited in number for rental, so please contact us in advance if you require one. A dry suit special is required for rental.

Nearby hotel | About 10 minutes by car to the shop

Hotel AZ opened in Ainan Town in 2025. It has over 140 rooms. It's close by, so I recommend it.

▽HOTEL AZ Google Map
https://maps.app.goo.gl/FrTmWGjWMC7sayCZA

More Articles and Outside Resources ｜Southern tip of Ehime, Ainan Town, Nishikai Sightseeing Boat

▽Ehime National Park Nishikai Sightseeing Cruise [1/4] | Shop Introduction

▽Ehime National Park Nishikai Sightseeing Cruise, official website here (Japanese, external site)
https://nishiumi.info/

• Table of Contents
• Overview of the entire facility | Saikai Sightseeing Cruise
• Greetings | Author
• Activity Introduction | Saikai Sightseeing Boat
• Recommended season: June to late October | Monsoons and water temperature
• More Articles and Outside Resources ｜Southern tip of Ehime, Ainan Town, Nishikai Sightseeing Boat

Overview of the entire facility | Saikai Sightseeing Cruise

Saikai Tourist Boat is a company with over 50 years of history, dating back to the 1960s, offering tours of the seas of the national park. On a sightseeing boat, you can observe schools of sparkling silver fish and colonies of coral, and in the summer you can travel to the uninhabited island of Kashima and enjoy marine activities such as snorkeling and sea walking. Scuba diving is also available. The sea here is home to an environment that is rare even on a global scale.

The area is surrounded by islands and ria coastlines, making it a rich environment not only on land but also in the sea. There are also many ridges in the sea, making it easy for fish to find hiding places, and one-quarter of the fish species found in Japan are found in this area.

There are many rocks and ridges in the sea, and coral grows on them. These corals act as hiding places for fish, creating an environment where even small fish can easily live. This in turn allows medium-sized fish to live there, which eat those small fish. One of the reasons for the large ecosystem pyramid is the large number of "undulations in the sea." The "abundance of fish" is a strength of Ainan Town's sea that is not found in many other places.

Greetings | Author

My name is Takahashi, and I'm a guide. I moved to Ainan Town from Tokyo in 2016. I currently run the Nishikai Tourist Boat. I use my experience at sea to perform a variety of tasks, including captaining the tour boat, as a diving instructor, helping fishermen with their diving work, and teaching marine classes. The sea around Ainan Town is very rich. Of course, I want to communicate this, but I also hope to share the joy of being in the water with as many people as possible.

Activity Introduction | Saikai Sightseeing Boat

Glass-bottom Boat

The boat that lets you see the ocean floor departs every hour from 9:00 to 16:00 every day. It's a short cruise of about 40 minutes, so you don't need to make a reservation. It's a convenient and recommended option if you want to observe the ocean without getting wet. The cost is 2100-2300 yen per person.

- Helpful tips
The 4:00 PM boat trips often have insufficient sunlight, making it difficult to observe the underwater scenery. Although it depends on the tide of the day, visibility is usually good in the morning. Also, the trip will be cancelled on windy days or other poor sea conditions, so please check the operation information posted on the official website of the Saikai Sightseeing Boat before coming. It is updated every day by around 8:30 AM.

Seawalker and snorkel tour to the uninhabited island of Kashima [held from mid-July to the end of August]

From mid-July to the end of August, you can cross over to the uninhabited island of Kashima. No reservations are required and the ferry operates every day from 8:30 AM until 4:30 PM, every hour.
The round trip fare is 1,000 yen per person plus your luggage allowance, and you can cross the island and swim in the sea.

- Helpful tips
Kashima is an island with an abundance of underwater creatures. It's best to prepare snorkeling gear beforehand to enjoy the trip. Water is sold at municipal facilities, but be sure to bring all the necessary items with you beforehand. The return boat departs Kashima at 00 minutes past the hour, so it doesn't matter what time you take to return. The boat has a capacity of 50 people, so if the capacity is exceeded, you may have to wait for an hour.

The Sea Walker is Kashima's best recommendation. No special qualifications are required, and you can walk through the ocean with a guide. All you need to do is put on a helmet, so you can observe the fish without getting your face wet. This tour allows you to search for fish in their natural environment without feeding them. In fact, Kashima is also designated as a special protected area of the national park, and the ocean is a place where fish tend to gather. The experience costs 6,500 yen per person plus a 1,000 yen round-trip fare to Kashima per person. Reservations are required, so please make your reservation through the official Nishikai Sightseeing Boat website - SeaWalker . The tour runs from mid-July to the end of August.

Scuba Diving in the National Park's Special Protection Areas

If you have a license, you can join a tour that takes you to areas of the national park that are particularly rich in marine resources. The sea around Ainan Town has many places with environments that are rare even on a global scale. The price is 14,000 yen/person for 2 dives or 18,000 yen/person for 3 dives (lunch included).
Reservations are required, so please make your reservation through the official website of Saikai Kankosen - Scuba Diving .

For more information about scuba diving, click here.

▽Ehime National Park Nishikai Sightseeing Cruise, official website here (Japanese, external site)
https://nishiumi.info/