A natural sponge is a type of aquatic organism that is used for cleaning and bathing. It is composed of a porous material that absorbs water and can be used to scrub surfaces. The two crossword solutions for the term 'natural sponge' are LOOFAH (6 letters) and loofa (5 letters). LOOFAH is a type of natural sponge made from the dried fibrous interior of a fruit, while loofa is a type of natural sponge made from the dried fibrous interior of a vegetable. Both are commonly used for bathing and cleaning.