sponge

Someone able to acquire new knowledge and skills rapidly and easily.

“she soaks up foreign languages like a sponge”

A follower who hangs around a host (without benefit to the host) in hope of gain or advantage.

Primitive multicellular marine animal whose porous body is supported by a fibrous skeletal framework; usually occurs in sessile colonies.

A porous mass of interlacing fibers that forms the internal skeleton of various marine animals and usable to absorb water or any porous rubber or cellulose product similarly used.

Ask for and get free; be a parasite.

Erase with a sponge; as of words on a blackboard.

Gather sponges, in the ocean.

Soak up with a sponge.

Wipe with a sponge, so as to clean or moisten.