To use a snorkel.
A snorkel parka.
A retractable tube fitted in diesel-engine submarines to allow sufficient ventilation that the engines may be used at periscope depth.
A hollow tube, held in the mouth, or mounted on and opening into a diving mask, used by swimmers for breathing underwater.
To perform a somersault.
Starting on one's feet, an instance of rotating one's body 360 degree while airborne or on the ground, with one's feet passing over one's head.