Found inside my house on the floor in 2022 and 2023; not since. Both bees (?) were released. Unidentified.
I have no idea whether this is an animal, fungus, or plant. To the touch, it feels like a mussel, and it is attached to the rock in the same way a mussel is attached to its shell. There were several on one part of the rock, in a place where the water from the rapids occasionally washes over without submerging them.