Moroiso

Moroiso on the Miura Peninsula is one of Japan's most data-rich cold-water macro sites, with local dive clubs maintaining species lists exceeding 130 nudibranch species across multiple decades of records. The site consists of a gentle rocky slope from 5 to 22 metres with extensive coralline algae mats, kelp fronds, and hydroid colonies that provide habitat complexity for some of Japan's rarest seaslugs. Japanese wobbegong sharks — a species endemic to Japanese and Korean waters — are a signature animal here, resting in shallow rock gullies at 8 to 12 metres and rarely disturbed by patient divers. Winter brings the best nudibranch diversity as cold water suppresses visibility-reducing plankton and triggers breeding aggregations.