This simple, inexpensive bottom sediment coring device consists of 1) a recoverable core barrel, check valve, buoyant chamber assembly; and 2) an expendable weight and casing assembly. The corer is dropped free and falls to the bottom. A simple release-delay timer then sets loose the core barrel and its buoyant float. The expendable weight-casing remains embedded in the sediments. The device has been tested in 700 fathoms off San Diego with excellent results. There is no depth limitation to the use of the free-corer.