GRENADES are not exactly synonymous with life-saving, but they have inspired a young Sydney designer to create an award-winning device that could save swimmers from drowning.

Sam Adeloju's design, named Longreach, with the unofficial name ''Buoyancy Bazooka'', shoots an emergency flotation device 150 metres out to sea. Made from hydrophobic foam, the buoy can expand up to 40 times its size on contact with water so the swimmer can stay afloat without risk the buoy will spring a leak. The device is also equipped with flares for night-time.

The idea came to Mr Adeloju during Army Reserve training, when his instructors demonstrated grenade and flare launchers. He also took the idea of adding a whistle from a popular toy called a Vortex.

''I realised how ineffective a [standard] life ring would be if the drowning victim was a great distance from their rescuer.