Purple Sponge Encrusting Seaweed

Description:

Pale purple sponge encrusting some seaweed that washed up on the beach. It was the only sponge and the only seaweed I found here, so I'm thinking that maybe the sponge made the seaweed more buoyant so it could wash ashore.

Habitat:

It was halfway up the shoreline of this beach made up of mostly empty oyster shells and lime rock near lots of mangroves