A sediment coring device containing a protected glass tube through which water flows freely during descent and which is forced by impact into the sediment. On hauling, a simple valve mechanism closes the top of the tube and the sample may be brought to the surface. The body of the sampler is a brass cylinder into which fits a thinner metal tube holding the glass sampling tube. When the glass tube is in position, it is closed by a rubber bung that comes hard against the upper surface of the main body of the sampler in the center of which is a hole.