Abstract: The apparatus includes a sample-holder comprising a tube (16) of thin aluminum, and a piston (12) slidable in the tube. The piston is mounted on a solid, robust piston rod (14). To drive the apparatus down to the depth at which the sample is to be taken, the piston and tube are locked together, and travel down in unison, most of the force of the hammer blows being taken by the robust piston rod. When sampling depth is reached, the piston rod (14) is uncoupled, and the piston (12) is restrained by means of a cable (36) to the surface; further hammering now drives only the tube (16) downwards, not the piston. The tube being thin, the drive force is must less, whereby the tube does not collapse, as the sample enters the tube.