Answer:
The ones in the sea are prickly, but the ones on the street might pickpocket you.
Oh how I love my dancing feet! They stay together - oh so neat. And when I want to walk a line, They all stay together and do double time. I count them up, ten times or more, And race on-off, across the floor.
They're actually great swimmers now, but later they will become excellent hoppers.
Face with a tree, skin like the sea. A great beast I am. Yet vermin frightens me.
Stealthy as a shadow in the dead of night, cunning but affectionate if given a bite. Never owned but often loved. At my sport considered cruel, but that's because you never know me at all.
I break away from my pack. I create holes in my victims. I can travel for miles and then disappear. I am part of a dying breed. What am I?