OK, you keep your bum!  This does mean it costs more muscle energy to digest food as it has to move against gravity, but your gut is longer,...

Quick win: no bum!  You can get away with a smaller gut, and eat, absorb the easy nutrients, and chuck up whatever's left, then go on to...

Each of your five arms develops arms of its own.  Those arms develop even smaller arms.  This repeats until your arms fill the gaps between ...

A neat, small central body with serpentine arms reaching out from it enables you to move rapidly across the ocean floor, grabbing on to what...

Getting bigger, longer, musclier, and thicker, you have a long, efficient gut, and can get all the nutrients out of your food.  You live thr...