Sting rays have a barb on the end of their tail. Skates have 3 pronged sharp barbs in lines all over their entire body. Ask any fisherman about their first encounter with a skate. Everybody has gotten stabbed trying to handle them atleast once. There really is no proper way to handle them(that isn't harmful to the fish).
What to the prongs look like? How long?
I once stepped on something pushing off the bottom to jump back on my board. I ended up with three long whiteish plastic looking barbs in my foot. They all broke off just below the skin surface. The longest one was about 3/4". It looked like someone stabbed my foot with a three pronged fork, and the prongs broke off in my foot.
Freaking hurt like a mother chucker. I never knew what they were, but always wondered. I even saved them for a while, in an old film container (weird I know). Does this sound like the prongs on a skate?
I have stepped on them out west, but my immediate reaction is to basically collapse. Like, take all pressure off of the foot where I feel the slimy creature and fall back as the impacting foot lifts up. A few close calls and it probably looks ridiculous, but that is how I handle any sea creature that I step on, just flop over and simultaneously remove all weight from the foot in question.... Its not an exact science, but thus far, it has been a maneuver that has allowed me to avoid impending doom.... Knock on wood. Ohh, and shuffling your feet obviously.... But doing that round here this time of year, lets your feet and legs just drag over all the giant jellies, but I guess jelly stings are not nearly as bad.... In this murky water, I usually get my feet up out of the water as soon as I can in the spring time. No telling what you might "bump into"....