A hydrostatic penetration device for placing on and penetration of the seabed comprises a housing (1) with a top cover (2) and a bottom cover (3), and a through-going vertical tool (4) for penetration of the seabed. The hydrostatic penetration device comprises at least one low pressure chamber (5), at least one hydraulic cylinder (6) with a vertically movable piston and piston rod (10) which can be driven to upward and downward movement by a flow of pressurised water from the surrounding water to the low pressure chamber (5), a clamping device (8) which surrounds the tool (4) and is connected to the piston rod (10), and which, during an upward and downward movement of the piston rod can be brought out of and into engagement with the tool respectively, and at least one weight (7) resting on the piston rod, which weight is vertically movable under the influence of the piston rod (10) and is arranged to transfer its weight to the clamping device (8) during a downward movement.