Any idea what this is?

[shogun1964]

Got this on a piece of live rock from the gulf on mexico. Its green and feels like rubber.

 

[meir]

Some kind of soft coral

 

[ebushrow]

is it flat?

 

[Maritimer]

It's a holdfast that once attached a bivalve of some sort to that rock. Resilient and durable, but not alive.

~Bruce