Senohama Reef is a boat-access artificial reef off Nishiumi in Ainan, Japan. More than 20 sunk iron boxes rest on a sandy bottom, creating a fish habitat that rewards relaxed loops, macro photography and nudibranch hunting. The box layout makes it easy to build a simple circuit, pause for close inspection and turn the dive around without needing a long swim. It is a site for close-range reef watching rather than big depth or current, so plan it as a calm local boat outing with compact terrain and lots of fish activity.