Without sounding stupid, you could, if you were a surfer, paint an 'eye' on the base of your surf board. Apparently this intimidates them. The device is a good idea, and not swimming with them PERIOD is a somewhat great idea! If you have an arm free, you could punch them really hard on the nose whilst they're chewing on your leg but seriously, swimming with the likes of reef sharks isn't too dangerous. Hanging around in the South Australian Bite or Frazer Island with flippers on - well, you need you'll need your head checking - so summing up where you're planning on taking a dip is good advise! Sorry if I haven't told you anything you didn't already know! Regards, One legged Captain Jim the Deep Sea Fisherman