Osezaki, Numazu: Diving the sheltered bay and outer reef

Osezaki presents a dual-faceted diving experience, centered around a unique peninsula that creates distinctly different conditions. The inner bay, locally known as 'Wan-nai', acts as a natural sanctuary. It's a spot where you can comfortably refine your buoyancy and skills without concern for strong currents or significant wave action, making it a primary location for entry-level training and certification dives. You'll find a mostly sandy bottom contrasting with small reef sections, offering diverse habitats ideal for spotting smaller creatures and practising navigation.

Beyond the shelter of 'Wan-nai', the peninsula extends into the open ocean, offering at least five additional dive points on the seaward side. The transition from the calm bay to these sites is immediate; you'll notice the change in topography as the seafloor becomes more rugged and exposed. One of these outer sites, 'Saki', is located near a shrine and requires a nominal entry fee, indicating its distinct access point and specific dive profile compared to the more readily accessible bay area. These outer sites are where Osezaki's unique pelagic potential truly unfolds.

A notable feature of Osezaki's outer sites is the regular presence of manta rays. These encounters are a significant draw, occurring frequently enough to make them a point of attraction. While specific depths or conditions for these encounters aren't always predictable, the fact that they are consistently observed here speaks to the site's oceanic exposure and the currents that bring these pelagic giants close to shore. You should maintain awareness of your surroundings and be ready for a chance encounter, particularly when diving deeper and closer to the open water.

The marine life at Osezaki extends beyond the larger pelagics. Deliberate night dives have revealed exceptional observations, such as ribbonfish (Ryugu no Tsukai), which are rarely seen in these waters and often found at significant depths. This indicates the biological richness of the site's deeper areas and the potential for unique encounters, especially during specialized dives. You might also find glass gobies perched on blue gorgonian corals, a reminder that macro life thrives here alongside the larger inhabitants, requiring a slower pace and keen eye.