Conditions & tides
Scored by DiveConnect's site-physics model
Marine forecast via Copernicus Marine. Score is a rule-based guide from swell/wind vs. the site's exposure — always dive your own assessment.
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About this site
One B (大根B) is a boat-dive site at Nishikawana in Tateyama on the Boso Peninsula, Chiba, four minutes from the harbour, with a maximum depth of 20 m. Entered from the B buoy, it is a valley between two large reefs; the main route, known as rockfish valley, has a bedrock floor and a sheer western wall covered in sea fans, with interesting life along the boundary between rock and sand. Suitable from beginner level. A guide rope runs along the bottom, so navigation is simple.
Marine life here
Confirmed by our research team, reported by independent divers, or observed nearby via iNaturalist — each entry is labelled with its source.
Pearl-spot ChromisChromis notataReported here · unconfirmed
Blacksaddle GoatfishParupeneus spilurusReported here · unconfirmed
Durable tips from divers — access, hazards, marine life, facilities. For day-of conditions, use the report tool in the conditions card above.
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