Unknown Critter

[Hangfire]

Thanks for the responses all. It does not appear to move, and to me it does kind of look like a tube worm. Actually, at first it reminded me of a flower bulb with a sprout emerging. the larger part at the base is sort of rounded. Not sure it's vermetid snail, although I'll watch to see if it moves. I'm really hoping it's nothing bad, as I already have a few apstasia growing on rocks, and two rather hairy crabs running around. . .