Koh Tao is one of the few islands in the world, that only has one tide (Diurnal tide) a day. Due to this unique feature the island doesn't suffer the same amount of tidal exchange that is common on the Andaman side (West cost) of Thailand.

This results in safe and calm diving conditions.

The only time that the island experiences any form of current is around the dates of the full- and black moons.