Freediving in Izu: Tokyo's Two-Hour Blue Escape

You can’t fly to Okinawa every time you need to get wet. The good news: two hours from Tokyo there’s a training bay where you surface facing Mt. Fuji — Osezaki on the west coast of the Izu peninsula, home base of the Kanto freediving scene.

Why Osezaki

The topography is perfect: the cape wraps around like an arm, sheltering an inner bay that stays calm even when the open coast is blown out — year-round trainability that almost nowhere else in Honshu offers
Real depth: a gentle slope runs from 5 m platforms down past 20 m — ideal for setting a line
Life that surprises: soft coral gardens, seahorses, autumn sardine storms, and the occasional legendary sunfish
The Fuji moment: on a clear day you surface to a full view of the mountain. Worth the train fare alone

When to come

Months	Water	Wetsuit	Notes
Apr–Jun	17–21°C	5mm	Visibility recovering, few people
Jul–Sep	22–26°C	3–5mm	Most comfortable; go on weekdays if you can
Oct–Nov	20–23°C	5mm	The hidden ace: clearest water, sardines, sunfish
Dec–Mar	15–17°C	5mm + hood	For the committed; peak visibility

Rule of thumb: Izu’s water runs one season behind the air. Don’t let a warm May afternoon fool you — the sea is still in early spring.

Getting there

Train: Shinkansen Tokyo → Mishima (50 min), then the Izuhakone line to Shuzenji and a bus or taxi to Osezaki. About 2.5 hours door to door
Drive (recommended): Tomei expressway → Numazu IC → the west-coast road. About 2 hours from Tokyo, and the coastal road is a destination in itself
With gear, drive or ride with your school

After the dive

The correct Izu formula is diving + onsen. Stop at Shuzenji Onsen on the way back, or hit Numazu’s seafood market. Leave Friday night, train Saturday and Sunday, soak, and be back in Tokyo by Sunday night — the standard Kanto freediver weekend.

Can beginners come?

Yes. The bay’s calm conditions are actually better for coursework than many tropical islands — our AIDA2 course runs here. Just set expectations: the water is Honshu green-blue, not Okinawa neon. For training value and access, though, Izu wins.

Want to plan an Izu training weekend? Talk to us.