Sepoi is one of the further islands from Tioman, hence it is not dived as frequently as the others. Often done as a drift dive around the island up and over the volcanic boulders.
Just off the northeastern edge of Sepoi Island is a submerged reef where sea fans, soft corals and sponges are all competing for space. Featherstars, worms and gastropods are all common on the protected reef. Fish life here includes moon wrasse, angelfish, butterflyfish, pufferfish and coral groupers.