I see my original query about what it felt like was not heeded. Come on Kev, grow some brass ones and take a feel! Heck, you can probably wear gloves and still determine whether or no it's a sponge or a tunicate.
TOUCH IT TOUCH IT TOUCH IT TOUCH IT TOUCH IT TOUCH IT
Okay. I finally found it, or another one again. I touched it. It was smooth, but not slimey or sticky, nor was it stretchy. It was muscular feeling, and reminded me of the way a conch feels, kinda rubbery and firm. Here's another image. Here's a link to the full sized photo so you guys can see more detail. It's kinda big.