A marine vibrator, comprising: a support frame; an auxiliary tank coupled to the support frame; and a plurality of pistons coupled to the support frame and adapted to receive a gas from the auxiliary tank, characterised in that each piston comprises: an actuated head; and an actuation mechanism adapted to move the actuated head, the actuation mechanism comprising: at least one pair of cam assemblies, wherein each cam assembly comprises: a shaft; and a plurality of cams coupled to the shaft, wherein each cam is coupled to the shaft at a location displaced from the center of the cam; a motor coupled to the shaft of each cam assembly; and a vacuum piston coupled to each pair of cam assemblies by two transfer members, wherein each transfer member is coupled between the actuated head and the vacuum piston such that the transfer member contacts the outer surface of a cam of the pair of cam assemblies, wherein synchronous use of the vacuum piston and the motors is adapted to stroke the piston. a support frame; an auxiliary tank coupled to the support frame; and a plurality of pistons coupled to the support frame and adapted to receive a gas from the auxiliary tank, characterised in that each piston comprises: an actuated head; and an actuation mechanism adapted to move the actuated head, the actuation mechanism comprising: at least one pair of cam assemblies, wherein each cam assembly comprises: a shaft; and a plurality of cams coupled to the shaft, wherein each cam is coupled to the shaft at a location displaced from the center of the cam; a motor coupled to the shaft of each cam assembly; and a vacuum piston coupled to each pair of cam assemblies by two transfer members, wherein each transfer member is coupled between the actuated head and the vacuum piston such that the transfer member contacts the outer surface of a cam of the pair of cam assemblies, wherein synchronous use of the vacuum piston and the motors is adapted to stroke the piston. an actuated head; and an actuation mechanism adapted to move the actuated head, the actuation mechanism comprising: at least one pair of cam assemblies, wherein each cam assembly comprises: a shaft; and a plurality of cams coupled to the shaft, wherein each cam is coupled to the shaft at a location displaced from the center of the cam; a motor coupled to the shaft of each cam assembly; and a vacuum piston coupled to each pair of cam assemblies by two transfer members, wherein each transfer member is coupled between the actuated head and the vacuum piston such that the transfer member contacts the outer surface of a cam of the pair of cam assemblies, wherein synchronous use of the vacuum piston and the motors is adapted to stroke the piston. at least one pair of cam assemblies, wherein each cam assembly comprises: a shaft; and a plurality of cams coupled to the shaft, wherein each cam is coupled to the shaft at a location displaced from the center of the cam; a shaft; and a plurality of cams coupled to the shaft, wherein each cam is coupled to the shaft at a location displaced from the center of the cam; a motor coupled to the shaft of each cam assembly; and a vacuum piston coupled to each pair of cam assemblies by two transfer members, wherein each transfer member is coupled between the actuated head and the vacuum piston such that the transfer member contacts the outer surface of a cam of the pair of cam assemblies, wherein synchronous use of the vacuum piston and the motors is adapted to stroke the piston.