Every year, Japan’s Ministry of the Environment checks the water quality of all bathing beaches across the country. This includes not only seaside spots but also rivers and lakes. Using that data, the Diamond Life editorial team created the 2025 ranking of prefectures with the most beaches showing top water quality.
How Japan Measures Water Quality
The survey covers 759 bathing beaches nationwide. Water quality is judged by several factors: Chemical Oxygen Demand (COD), which shows pollution levels; fecal coliform bacteria counts; water clarity; and whether oil slicks are present. The lower the COD, the cleaner the water.
Beach Categories
Japan sorts its beaches into five groups: Suitable (AA, A), Acceptable (B, C), and Unsuitable. Good news—this year, none of the beaches were labeled “Unsuitable.”
Top-Rated Beaches
The ranking focuses on 471 beaches that earned the highest rating of “AA.” These were then sorted by COD values. Only two beaches managed to stay in the top ten from both 2024 and 2025.
Beaches with Ultra-Low COD
Eight beaches stood out with COD values under 0.5 mg/L. They include:
- Four in Okinawa Prefecture
- Three in Shizuoka Prefecture
- One in Akita Prefecture
Spotlight on Okinawa and Numazu
Japan’s cleanest beaches include four in Onna Village, Okinawa (Sunmarina, Tiger Beach, Renaissance, Manza Beach), one in Semboku City, Akita (Lake Tazawa), and three in Numazu City (Senbonhama, Ose, Hirasawa).
Onna Village shines with more than just those four. Moon Beach and Rizzan Sea Park also show excellent water quality. Numazu City deserves mention, too. Even though it has one fewer top-ranked beach than Onna, Numazu places five beaches in the top ten. Mitsu Beach even landed at number 12, and overall, the city’s beaches are consistently strong.
Landlocked Prefectures with Clean Lakes
Some inland prefectures—Tochigi, Gunma, Saitama, Yamanashi, Gifu, and Nara—had no beaches listed. But Nagano and Shiga, despite being landlocked, earned AA ratings thanks to their lakes. Shiga stands out with four beaches on Lake Biwa, rivaling coastal prefectures in presence.
Other Prefecture Highlights
Among coastal areas, Miyagi had just one AA-rated beach, and Toyama had three. Saga, Kōchi, and Aichi each had four, tying with Lake Biwa. Surprisingly, Kagawa and Osaka had none at all, proving that simply having a coastline doesn’t guarantee clear water.
Japan’s Top 33 Cleanest Beaches
Below is the full list of the top 33 beaches with the cleanest water in Japan. Whether you’re planning a summer trip or just curious, these rankings show where the water is at its best.
Safety First
While Japan’s beaches are beautiful, water activities always carry risks. Drowning incidents happen often, so it’s important to stay alert. Keep an eye on the weather, take precautions against heatstroke, and enjoy the water responsibly.
