Abstract: An underwater lighting unit (1) for marine or other underwater use incorporates LEDs (13) as the light source and provides an array of LEDs (13) mounted against the back wall (11) of a metal or thermally conductive plastic housing (10) which utilizes the cooling effect of direct contact between the water and the housing to dissipate the heat generated by the LEDs (13) in use. The LEDs (13) each have an associated collimator (20) protected from contact with the water in which the unit (1) is to be immersed by a sealed glass screen (22), and each LED may be from one to three watts or more in power. There may be 30 or more LEDs (13) and associated collimators (20) in each lighting unit (1). The lighting unit (1) may be mounted in a cofferdam (2) of a marine vessel, directly against or slightly forwardly of the back wall of the cofferdam, or may be surface-mounted on the hull (3) of the vessel directly against or slightly spaced from the hull (3) and below the waterline.

Abstract: A bath 10 is provided with a plurality of air nozzles 17. Air is supplied to the nozzles to bubble through water in the bath. To ensure that water does not remain in the nozzles after use of the bath, means 83,85 responsive to the passage of water from the bath is arranged to activate the air supply means 81 after water has left the bath to blow any such water out of the nozzles 17. The responsive means may include a time delay 85 so that the air supply means is not activated until a period after the passage of water from the bath.