A stone I brought from White Rock, holding barnacles for my trophon snails, also carried this red-wine fuzz:
Soft, red cushion in my favourite shade.
I think it's an encrusting sponge, although it could conceivably be another of those invasive tunicates. (They were interesting and pretty, but I had to get rid of them; not an easy task.) I'll keep an eye on it as it grows.