Coral reef at AoPong beach is probably the best off shore reef at Koh Mak. Just 30 m from the beach (depend on the tide) you can watch the underwater life. There are various types of hard and soft corals (sponge, massive, table, mushrooms, digitate), fields of sea grass, various fish (puffers, groupers, parrot fish, butterfly fish, blue spotted sting rays, needle fish), sea cucumbers, various types of snails and crabs, sea urchins and others. Water temperature is very comfortable (around 29C) so you can spend hours in the sea. Visibility underwater varies between 3 m and 20 m and depends on the tide and weather conditions.