Thomas Reef is the smallest of the four Tiran reefs, sitting between Woodhouse to the north and Gordon to the south. What it lacks in size it makes up for in drama: the walls are sheer, the soft coral and gorgonian growth are among the best in the strait, and the current can be strong and unpredictable.

The site is known for the Thomas Canyon, a deep cut that runs along the eastern wall and drops well past 40m. It is a spectacular feature and a serious one. The canyon is a technical and deep-experienced dive only, with a real risk of narcosis and of losing track of depth against the wall. Most divers stay shallower and work the soft coral on the upper wall, which is reward enough.

Thomas is exposed and the current rarely lets up. Dive it as a drift, stay close to the reef, and treat the canyon with respect or leave it for another day.