Holothuroidea

Getting bigger, longer, musclier, and thicker, you have a long, efficient gut, and can get all the nutrients out of your food.  You live through several stages in your life now: tiny worm, little star, bigger star, until you become so thick and muscled that you tilt back and begin to look like a worm again, but a huge, thick worm, the size and shape of a common vegetable: you are a sea cucumber.

You still have radial symmetry, but unlike your sister species, your axis reverts back to horizontal, and you crawl or float or swim along with two 'legs' down, two to the sides. and one on top.  You secret a poison called holothurin which keeps you safe from many predators.  You mostly eat whatever detritus you find on the bottom, or whatever floats past you in the current.  Different species range from a few millimetres long to a whole metre long, and you live throughout the seas, although you are at your most dominant in the deep sea.