I used to have one when a Sea Ranger (one of the things you could do when you got too old for Girl Guides!)Then you could buy a bosun's whistle in Scout or Guide shops and they weren't that expensive. Didn't find it that hard to play: it largely hinged around blowing pressure and use of the hand cupped around the instrument. Mine got lost in one of the family moves, but I still have my Sea Ranger hat - great for any fancy dress nights involving sailors! Ahoy there, me hearties!