Diving Japan in Summer: Where to Go in July & August
Summer is Japan’s diving high season. From late June the warm Kuroshio current pushes north along the Pacific coast, water temperatures climb into the mid-20s°C, visibility opens up, and some of the country’s most sought-after encounters — dolphins, mantas and hammerheads — come into their best window. Here’s where to point your fins in July and August.
Around Tokyo: the Izu Peninsula & East Izu
The closest option to the capital is the Izu Peninsula. Summer brings warm, clear water to the East Izu coast — shore sites like Osezaki and IOP are ideal for training and relaxed fun dives, and tropical strays ride the current up from the south. It’s the perfect weekend escape before committing to an island trip.
The Izu Islands & swimming with wild dolphins
Out in the Izu Islands, summer is prime time. The headline act is Mikurajima, one of the Izu Seven Islands, where a resident pod of wild bottlenose dolphins gathers from spring through autumn — the dolphin-swim season peaks in the warm months. Neighbouring Kozushima and Hachijojima serve up clear blue water, big schools and volcanic underwater terrain.
Far south: Ogasawara
A 24-hour ferry from Tokyo, Ogasawara (the Bonin Islands) is Japan’s subtropical frontier — dolphins, sharks and, in summer, the chance of pelagic action in gin-clear water. See the dive sites and the wartime wrecks of Ogasawara for what awaits.
Okinawa & the far south-west
Okinawa dives all year, but summer delivers the calmest seas for its reefs, caves and manta cleaning stations. Keep going to Yonaguni, Japan’s westernmost island — while its famous hammerhead schools are a winter draw, summer offers warm, benign conditions to explore the enigmatic underwater monument.
Plan your summer dive
- Water temperature: roughly 23–28°C on the Pacific/southern side; a 3mm wetsuit is plenty for most.
- Visibility: at its yearly best — often 15–30m around the islands.
- Book early: July–August is peak season and Japanese holidays (Obon, mid-August) fill boats and ferries fast.
- Watch the weather: typhoon season overlaps summer — keep a flexible day or two in your itinerary.
New to diving here? Start with our dive destinations overview and the maps of Japan, or pick a style with our beach, drift and night diving guides.
← Back to the Dive Japan Journal, or explore dive destinations and maps of Japan.
