The mix of temperatures in the waters around Japan mean that the marine life available to see is simply unbeatable: enjoy over 3000 species of fish, firefly squid, angelfish and stunning anemones near the reefs. You can even see sharks patrolling the depths in large schools. Head to Okinawa for supreme dive diversity, including caves, tunnels, drops and wrecks as well as WWII wrecks and the Manta Scramble at Ishigaki Island.