Stewart Island - Stewart, or Ba Wei, Island lies north west of Cavern Island in the Mergui Archipelago and its main feature from a diving point of view is a smaller islet at its southern end with a spectacular large hole in it that makes for great photo opportunities, even above the water.
You can descend down the steep walls on either side of the small island and make your way to the other side through one of many large swim-throughs that are filled with large schools of snappers and fusiliers. Be aware of the strong surge and currents that can be present when you attempt the cross over.
The walls are covered in clams and sponges, making for a vibrant and enchanting scene. The wall is peppered with many caverns in which you can find juvenile nurse sharks, Here and in the smaller holes and crevasses, watch out for little crabs and all sorts of shrimps, including boxer shrimp and Durban dancer shrimps scuttling this way and that. Around the sandy bottom at about 25m, look out for patrolling black- or white-tip reef sharks on the hunt for tasty morsels of food.
As you can imagine, a dive site like this which has interesting features like swim-throughs, crevasses and caverns, plus all manner of crustaceans and other macro-life, is a popular spot for a night dive, conditions permitting.