Crabs, Prawns plus; Decapoda

Meaning “10 legged”, the order Decapoda breaks down into a bunch of infra-orders:
Anomura – hermit and porcelain crabs, plus the squat lobsters;
Axiidea – aka burrowing, ghost, or mud shrimps;
Brachyura – the “true” crabs;
Caridea – most of our prawns/shrimps;
and Stenopodidea – the “boxer” shrimps.
…many weird and wonderful creatures that you can meet when SCUBA diving around Koh Phangan.

Hermit and Porcelain "Crabs" plus a Squat Lobster - these crustaceans have longer bodies than the true crabs, and properly use only 8 of their legs. (2 Albums, 1 Gallery)

Just one - Trypaea australiensis. Seen once only because they live beneath the sand.

This infra-order contains most of our generally crab-shaped Decapods, with only 1 or 2 odd ones! (3 Albums, 6 Galleries)

Technically speaking, these are the "true" prawns and shrimps. (2 Albums, 2 Galleries)

This large cleaner shrimp is quite confident and makes a great photo subject.