The Burma Banks

The Burma Banks are a collection of submerged seamounts located roughly 180 km north-west of the Similan Islands, in international waters far offshore of the Mergui Archipelago. The name was coined by dive shop owners in the late 1980s, and the area was first dived in the early 1990s after Phuket-based liveaboards used early GPS equipment to pinpoint the banks' positions — nautical charts of the time did not accurately record them. Five sandy banks were eventually located, four of which were dived regularly: Roe Bank, Rainbow Reef, Big Bank, and Silvertip Bank.

The terrain consists of fairly flat, broad plateaus typically around one kilometre in diameter, surrounded by open sea and water exceeding 300 m in depth. Most plateaus top out at 21–24 m, with Silvertip Bank being the shallowest, reaching within 15 m of the surface. There are no walls — only gently sloping edges — and the bottom is sand. Because the shallowest areas still sit at 21–24 m, bottom times are short; Nitrox is commonly used to extend them.

The banks sit close to deep open water, making them a good place to encounter pelagic predators such as rainbow runners, bonito, and dogtooth tuna. Sharks are the main draw: at least nine species have been recorded here, with silvertips historically the most common, alongside occasional rare sightings of tiger sharks and scalloped hammerheads. Shark fishing in the early 2000s severely reduced silvertip and nurse shark numbers, though reports from around 2018 noted increasing juvenile shark sightings.