Also known as Clam, Derasa Clam, Giant Clam, Smooth Giant Clam, Southern Giant Clam.
Found in sheltered waters, over soft bottoms of back reefs, reef flats, fore reefs and lagoons.
Varies in colour.
They feed on plankton.
Length - 50cm
Depth - 0-20m
Widespread Indo-West Pacific
The Necklace Clam is a triangular in shape and the shell edges are wavy instead of convoluted.
Most Bivalves are permanently anchored in fissures or depressions in the rock surface of the reef, some may become covered in algae and other marine life.
Other Bivalves swim free, either by a well developed foot or propelled along by a jet of water from their mantle cavity. (edit) Ref: https://en.wikipedia.org/wiki/Tridacna_derasa