"Sea spiders" or pycnogonids, are members of Phylum Arthropoda, along with land spiders. Besides living underwater, sea spiders differ from their land cousins in other ways-- they don't spin webs, and may have from four to six pairs of long segmented legs, versus four pair for land spiders. Of the 600 or more species of sea spider most are very small, ranging from 1/100 inch to about 20 inches across. This one is small, only about 3/8 inch across. The largest sea spiders reside in the deep ocean.

About 500 pictures of the shrimp, lobster, black tigers, mantis shrimp... on the world

Crabs are various species of decapods Decapods. They are crustaceans with five pairs of legs, the first pair modified to form a pair of pincers, a flattish shell, and a short, broad abdomen folded under its thorax. There are two main groups of crabs: the Brachyura or true crabs, and the Paguroidea, or hermit crabs. Crabs are related to lobsters and shrimps

About 100 images, common crustaceas of Viet Nam.

About 200 pictures of the marine fishes on the Viet nam