A float (1) comprising a hollow pneumatically pressurisable ovoid shell (5) is provided with a damping plate (12) extending laterally outwardly around the shell (5) for damping vertical upward and downward movement of the float in water during stormy conditions, thereby minimizing the effect of the buoyant upward propulsion force acting on the float when the float is submerged in stormy conditions. A keel (18) extends downwardly from the float (5) for minimizing rolling movement of the float (1). A pair of coupling plates (22) extending from front and rear ends (19,20) of the shell (5) facilitate coupling of the float (1) between a pair of spaced apart tethering ropes used in mussel growing. A plurality of the floats (1) may be secured between a pair of spaced apart tethering ropes at spaced apart intervals along the tethering ropes for supporting the tethering ropes so that crop ropes impregnated with mussel spawn may be suspended from the tethering ropes for growing mussels. A navigational buoy (60) is also disclosed, which comprises a lower float (61) and a pillar (62) extending upwardly therefrom for carrying navigational and other instrumentation.