Related to sea stars, the sea cucumber pretty much looks like what it's called. The over-sized pickles are usually found laying on the sand. They move very leisurely over the bottom and sometimes grub into the sand.

They are pretty non-descript until you look very closely. Like corals, startling details, patterns and colors emerge, as in this extreme close-up of the warty skin of a sea cucumber at Bari Reef.

They either eat sediment or strain plankton from the water. Their mouth has no teeth but in at least one variety, the anus is equipped with five teeth. Some also breath through their anus, sea water being drawn in and then expelled.

And it has one more trick up its, er ah, sleeve. When under attack, the sea cucumber can eject its internal organs through its anus, as well. The attacking predator then gives up on the robust outer skin and feeds on the organs, giving the sea cucumber time to flee, where it will find shelter and regenerate its digestive tract.

Pretty resourceful survival behavior for such an apparently simple creature.