The most popular Koh Phi Phi diving sites lie under the sea at the two islets just to the south of Koh Phi Phi Lei, home of the famous Maya Bay. Koh Bida Nai is the smaller of the two rocky limestone formations which jut vertically out of the Andaman Sea. Its name means 'Inner Father' in the local dialect and it is visited by almost every PADI scuba diving centre in the area. Koh Bida Nai offers among the best fun diving in Thailand, but can also accommodate novice divers and all levels up to professional.

• Easy diving for all levels
• Clear, current-free water most of the year
• Sharks seen every day
• Lots of healthy marine life and corals

The topography (underwater landscape), healthy and diverse reef life, and general sea conditions make Koh Bida Nai a very predictable, yet enjoyable diving site just a short trip from Koh Phi Phi. Its location makes it ideal for Phi Phi PADI diving operators to use it for local fun dives, as well as Discover Scuba Diving (introductory dives). It is also used for all or part of many other PADI courses. In addition, Bida Nai is visited by Phuket diving operators, those from Koh Lanta, Krabi and other locations around the Andaman.

Koh Bida Nai is an excellent diving site for a number of different reasons. Firstly, its topography allows for adventurous yet safe diving practice. It is not boring for advanced and professional divers, nor is it too challenging for those who have never dived before. The walls of the limestone outcrop/islet descend vertically to depths of approximately 30 metres, depending on the section of the dive site. However, there is also lots to see right up to the surface, thus keeping divers happy regardless of their depth, and even catering for snorkellers who can't dive, or who want to stay in the water during their surface interval. Underwater between Bida Nai and its partner, Bida Nok, lies a large flat area covered in Staghorn Coral, known as Fantasy Reef. Around the islet of Bida Nai the currents and visibility are more often than not easy and enjoyable. There are a few swimthroughs and lots of nooks and crannies to explore. There are no exciting drop offs or caves, but the general topography of Bida Nai makes it an enjoyable but not overly-challenging dive site.

The marine life at Bida Nai is very similar to other Phi Phi diving sites, such as Bida Nok and those at the famous Koh Phi Phi Lei. Although large and exciting pelagic cartilaginous fish such as Whale Sharks (Rhincodon typus) and Manta Rays (Manta alfredi) have been sighted here, appearances are a surprise and a treat. However, it is quite common to see Leopard Sharks (Stegosoma fasciatum) resting on the sea bed after a night's hunting. These gentle bottom-feeding sharks are not at all dangerous and quite used to divers. However, harassing them causes them to get up and swim away, which is neither fair to the animals nor the next group of divers to come along. Bamboo Sharks (Hemiscylliidae) are another species which can be found resting, but these smaller sharks usually hide under a rock. Reef sharks, such as Blacktip Reef Sharks (Carcharhinus melanopterus) are shy, but can sometimes be seen in shallow and mid depths, especially early in the morning. Whitetip Reef Sharks (Triaenodon obesus) are far less common here at Bida Nai, but sightings have been reported. These slender and beautiful sharks are generally found deeper than the stocky Blacktips. You are also likely to see a Blue-Spotted Stingray (Neotrygon kuhlii) and have a small chance of finding a baby Nurse Shark (Ginglynostoma cirratum). The range of reef fishes and invertebrates to be seen at Bida Nai when diving is vast, right down to tiny creatures which are favoured by those looking to find and/or photograph macro marine life. Less-observant divers and those in a rush can dive at Bida Nai dozens of times without ever seeing a Harlequin/Ornate Ghost Pipefish (Solenostomus paradoxus) or a seahorse, but they are there. Divers just need to slow down and keep their eyes peeled. Fun divers should pay extra attention to their Divemaster during the pre-dive briefing, in order to understand the signals for small critters. This is because when underwater the Divemaster can point at something small and special, giving signals about its identity, but the fun diver just can't see it.

This review of the Koh Phi Phi diving site known as Bida Nai is as accurate and informative as possible. We have dived there on many occasions and enlisted the help of others. There are dozens of commonly-seen reef fish at Bida Nai which we have not mentioned. Although we have done our best to supply the most factual, relevant and informative information, we appreciate that we are not perfect. We welcome comments, however small or critical. Please just post in the box below. We also have a diving forum which is free and easy to join and use.