Mantis shrimps are perhaps the most alien-looking creatures in the sea.  Armed with powerful forearms called dactyls, they come in two varieties.  Spearers, whose dactyls are lined with many needle-sharp spines for grabbing fish, and smashers, whose dactyls are adapted for crushing the shells of clams, snails and crabs.  Their compound eyes are mesmerizing when seen in extreme close-up.

*Click on Sand Mantis for video*