The waters surrounding Zamami Island lie within Keramashoto National Park, designated in 2014 partly because the coral reefs here are among the most intact in Japan. The visibility regularly exceeds 30 metres — exceptional even by international standards — and the reef systems have been largely spared from the bleaching events that have damaged corals further south. Dive sites around the island range from shallow coral gardens accessible to snorkellers to walls and channels with strong currents for experienced divers.
Several dive shops operate out of Zamami port and offer guided reef dives, fun dives for certified divers, and introductory dives for beginners. Common sightings include manta rays (more common in summer), sea turtles year-round, large schools of fusiliers, lionfish, and octopus. The uninhabited islands of Gahi and Agenashiku, reached by a five-minute boat ride, have some of the best reef access on the island. Equipment rental and guided tours can be arranged at the dive shops near the port.