KEEPS WATER OUT, the Impulse has two valves: if a wave breaks over the snorkel, the upper valve directs most of the water out before it reaches the mouthpiece.
But if water does get past the first valve, it will drain out through the lower valve.

CLEARS EASILY, in the unlikely event that you would need to clear the reservoir below the mouthpiece, all it takes is a gentle puff of breath.
The flex section allows for easy positioning and will drop away when not in use.