“It is a survival whistle that is a completely original design. I designed it to be rugged, easy to make and carry, have a great design and most importantly be very loud. It is designed to be able to get you noticed in all conditions.
For ruggedness testing I spiked it into the pavement as hard as I could repeatedly. Then I ran it over with my car twice. Finally left it in a glass of water for two hours to make sure that it would not sink and would drain and whistle immediately after taking it out. It still whistles.”
-https://www.thingiverse.com/thing:1179160 (Original creator)