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Tateyama · Japan · Reef

Nishikawana One

Ōne, the big root rock off Japan's cod hole

Nishikawana One is a boat point at the tip of Tateyama, built around Ōne, a large rock formation whose name means big root. Rocky reef, boulders and sand make up the bottom. Nishikawana is fed year-round by the warm Kuroshio Current and is known as Japan's cod hole for its longtooth groupers.

Also known as Ōne, Buoy A.

Where it is and how deep

Depth profile of Nishikawana One: typical dive to 25 m (to 82 ft) 18 m · Open Water30 m · Advanced40 m · Recreational limit25 mtypical dive
Depths on a shared scale to 40 m (130 ft); dashed lines mark common certification limits.

34.9616° N, 139.7519° EApproximate position — the dashed circle shows where the site lies; your operator's briefing has the mooring.

The dive

Divers enter at Buoy A and head toward Ōne across a bottom of rocky reef, gorota boulders and sandy patches. Most of the dive stays around 15 to 16 m, and the deepest ground reaches 25 m. Nishikawana holds more longtooth groupers, known locally as moroko, than any other dive point in Japan.

Marine life and season

  • Groupers
Month-by-month season rating for Nishikawana One
JanFebMarAprMayJunJulAugSepOctNovDec
GoodGoodGoodGoodPrimePrimeGoodGoodGoodGoodGoodGood

Season follows Tateyama: Boats run all year; May and June bring the eagle ray schools that can number in the hundreds.

Know before you go

  • The current over the reef is often strong and can run fast at times, so the site suits intermediate and advanced divers.

Questions divers ask

What certification does Nishikawana One need?+

Advanced Open Water. The bottom reaches 25 m and the current is often strong, so the site is best left to intermediate and advanced divers.

Sources

  1. Nishikawana One — ScubaGo
  2. Scuba Diving in Chiba: Discover Japan’s Boso Peninsula Dive Sites — PADI Blog
  3. Nishikawana Ocean Park — Nishikawana Diving Service

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