Offshore crane

The invention relates to an offshore crane compensated for local water movement. The crane has a substructure, a boom, and a heave device comprising a winch, a hoisting cable, and a gripper for carrying a load. The boom has a fixed end supported by the substructure and a free end. The hoisting cable extends from the winch, along the boom to the free end of the boom, and suspends from the free end of the boom freely to the gripper. At the fixed end, the boom is configured for slewing with respect to the substructure around a slewing axis and for luffing with respect to the substructure around a luffing axis, the luffing axis being perpendicular to the slewing axis. In order to compensate for local water movement, an xaxis translational movement, y-axis translational movement, z-axis translational movement, xaxis rotational movement, y-axis rotational movement and z-axis rotational movement are measured; on the basis of these measurements an x-, y-, and z-translation, experienced by the free end of the boom due to movement of the substructure, are determined; and these determined x-, y-, and z-translations are neutralized by correspondingly actuating the actuator system such that the position of the gripper is kept motionless. The invention further relates to a method for compensating such crane for local water movement.