I took this photo on Fort Myers Beach in South Florida. It is a live sponge. There were LOTS of them on the beach after a storm. The sponges that were already dead quickly turned a dark brown. Inside the sponge is a fibrous network that acts like a skeleton, holding it up, and giving it shape. When the sponge dies, the remains of the living cells decompose, leaving behind the fibrous material that people think of a s sponge.