I intended to tie this to my lifejacket for paddleboardin' and kayakin'. I adapted the design to work well with a fat nozzle because that's what I've got. As a bonus, the double-thickness walls increase crush-resistance.

My adaptations in the attached project are in the Y-axis scaling and the XY size compensation (aka horizontal expansion).

Unfortunately, this whistle turned out neither as loud nor as compact as my Phlat Keychain Whistle; so I'd go with that one instead.