There, the divers saw both more fish overall and a greater diversity of species, including tropical ones such as the blue damselfish (Pomacentrus coelestis) and the cutribbon wrasse (Stethojulis interrupta). Tropical invertebrates included the long-spined sea urchin (a species of Diadema).

“There were so many sea urchins as they did not have predators,” says Masuda.

These tropical species weren’t seen at the other two sites, even though winter temperatures there were only slightly lower, at 12.3°C and 11.7°C.