Abstract: A buoy (1) has a main body (5) and a moveable mass (2) positioned inside the main body. The buoy may be tethered to a submarine vessel and used as a communications buoy. The buoy may be configured for floating in a generally upright orientation at the water surface (7) in a position ready for communication, when the mass (2) is in a first position (FIG. 1a) in which the center of mass is offset from the center of buoyancy to improve stability in the water. The buoy may be configured for being towed underwater at speed, when the mass is in a second position (FIG. 1b), in which the center of mass is closer to the center of buoyancy, to improve towing stability in the water, thereby allowing the buoy to be towed with its long axis substantially aligned with the direction of motion, thereby reducing wake/plume in the water.

Abstract: A buoy (1) has a main body (5), and a moveable mass (2) positioned inside the main body. The buoy (1) may be tethered to a submarine vessel and used as a communications buoy. The buoy (1) may be configured for floating in a generally upright orientation at the water surface (7) in a position ready for communication, when the mass (2) is in a first position (FIG. 1a) in which the centre of mass is offset from the centre of buoyancy to improve stability in the water. The buoy (1) may be configured for being towed underwater at speed, when the mass (2) is in a second position (FIG. 1b), in which the centre of mass is closer to the centre of buoyancy, to improve towing stability in the water, thereby allowing the buoy (1) to be towed with its long axis substantially aligned with the direction of motion, thereby reducing wake/plume in the water.