Giant Sea fans are a common sight at many of the Koh Lanta dive sites, including the Bida islands, Phi Phi, Koh Haa, and Koh Rok.
The six species in this family have strengthened their inner skeletons with gorgonin to such an extent that they are far less brittle than other related soft corals.
There are three genera in this family. The genus rosgorgia contains a single species which is confined to Antarctic waters, and the remaining two are tropical. These two genera can be easily distinguished by their growth patterns, and neither have symbiotic algae.
The Giant Sea fan genus Subergorgia contains three species which are tree-like with stems and side branches. All branches have a narrow but deep groove running along their entire length.
The genus Anella contains two species which are fan-like with branches arranged in a net-like manner with a very small mesh. Due to the much-strengthened inner skeleton, these corals can grow several meters in height and diameter, with the central branches being much thicker than the others.
The colour of the branches varies from dark red (rare) to yellowish-orange or cream-coloured.