save the manatee!!!

ok before you all call me a tree hugger, these poor animals are always getting run over by boats and it's kind of sad. why can't they make a propeller cover kind of like an oscillating fan(like the one in your house) so that if it bumps into a manatee it won't cut it up? i understand that seaweed and stuff is a concern getting tangled up in a cover but it doesn't really have to be more than a single cincular ring around the propeller and a couple other pieces just to hold it together... :noidea: just thinking here... if anyone copies this idea and makes money off it just cut me in on a little bit :P