A geophysical measurement device is provided for exploration of natural resources of the floor in an aquatic domain. The device includes a frame designed to rest in a stable manner on the floor of the aquatic environment, at least one buoyancy caisson resting on the frame, measurement instruments. The measurement instruments including: at least one sensor making it possible to measure locally at least one of the components of the magnetic field; an analogue and/or digital data acquisition and processing device; and a source of energy supply of the sensor and of the data acquisition and processing device. The at least one sensor is contained inside the buoyancy caisson.