Together with Koh Bida Nok, Koh Bida Nai sits within a marine park and has some of the best dive sites in Phuket. The dive site here at Koh Bida Nai is considered the little sister of the two but it is equally blessed with mild currents and visibility of up to 20 meters. The depth of this site goes to about 30 meters, and like its sister dive site, it is made up of a steep limestone wall that drops to the sea floor. It is covered in many colourful corals; many Gorgonian sea fans, and also has many swim throughs.

The marine life is very similar to Koh Bida Nok and so divers should expect boxfish, batfish, barracuda, pufferfish, porcupine fish, sea snakes, groupers, and lionfish. There is a garden of staghorn coral at this site, and so also common are angelfish, scorpionfish, sweetlips, trevallies, snappers, and cuttlefish.

This site has many more anemones and so more anemone fish but divers are also likely to spot turtles, and sleeping leopard sharks on the ocean floor. Blue spotted stingrays and black tip reef sharks can be seen lurking on the sandy bottom as well.