The pressure wave can be detected by a mine, however. The faster the ship is moving, the greater the effect. Pressure influence sensing. This too allows the mine to distinguish between many different types of targets. Acoustic influence sensing.
Bottom mines rest on the ocean floor.
They can be deployed from aircraft, submarines or ships, although deployment from surface ships is rare. In shallow water they are effective against surface ships and in deep water against submarines. Aircraft deployed bottom mine. The anchor keeps the mine from drifting. Submarine deployment of mines.