Kashiwajima is a small bridge-linked island in Otsuki, southwestern Kochi Prefecture, famous for water so clear that locals say 'boats look like they're floating in mid-air' when viewed from the bridge above. Sitting where the Bungo Channel meets the Kuroshio Current, it hosts roughly a third of all fish species found in Japan, and its shallow inner bay (about 1-6m deep) lets snorkelers get close to coral patches and dense schools of colorful reef fish without diving deep, making it one of Japan's premier, beginner-friendly snorkel and dive destinations. As of July 2026, dive shops and boat tours are running through the summer peak season, though the island's rising popularity has brought tighter rules on safety and environmental protection.
Shallow, calm white-sand entry near the bridge and inner bay, ideal for beginners and families
Ryugahama Beach, where coral patches and reef fish are visible right from the shoreline
Exceptional 15-25m visibility, famous for the 'floating boat' view from the bridge above
Rich biodiversity, with roughly a third of Japan's fish species recorded around the island
Glass-bottom boats and clear kayaks let non-swimmers view the reef from the surface
Good to know
SafetyCurrents outside the bay can shift quickly because of the Kuroshio Current — stay inside the marked swim buoys, since conditions beyond them can pull swimmers offshore.
SafetyDive boats and fishing boats use designated lanes that get busy in peak season, so snorkelers should mark their position with a buoy or flag and never enter boat channels.
SafetySea urchins and stinging coral live on the shallow reef — avoid touching or standing on rock or coral, and consider gloves or a rash guard for extra protection.
SafetyJumping from the bridges is officially banned by the Otsuki Tourism Association after real injuries occurred there — do not jump into the water from either bridge.
SeasonLate summer into autumn (roughly August-October) brings typhoon passages and occasional jellyfish blooms afterward, so check the latest marine and weather conditions before heading out.
RulesNo littering on the beach or in the water — pack out all trash, and note that a small per-visitor environmental conservation fee supports coral protection (confirm the current amount locally).
MannersNever stand on or touch the coral, and don't feed or chase the fish and other marine life — the shallow water makes accidental contact especially easy.
Practical info
From Kochi Ryoma Airport, public transit runs via train to Sukumo Station and then a local bus, roughly 3 hours total; by car it's about 40-45 minutes from Sukumo Station. Snorkel-set rental and boat tours are offered by local dive shops and are best booked ahead; fees, hours, and the environmental fee change seasonally, so confirm current details with the Otsuki Tourism Association or a local shop before you go.
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