Draw attention to yourself. The whistle sends a very loud acoustic signal that can be heard even from a great distance.
The pitches of the two tones fulfill the standard for life vest whistles, DIN ISO 12402-8. This ensures you can be heard clearly from far away, even if there is ambient noise.
The emergency whistle is made of robust PA6 plastic, and therefore extremely lightweight. It is waterproof and floats in the water.