Eh, blowing air out after is kinda the same reflex. And decent seawater is basically netty potting yourself everytime you go under. I was in a situation to go to the beach every day for a year straight, and it was the best my allergies have ever been because at least once a day I was flushing it out with warm seawater.

Keep in mind, the alternative here is wearing nose plugs during prolonged physical activity. Restricting breathing during physical exertion is going to rub a lot more people the wrong way.

So I'm surprised people would deal with that, over the chance of some water going up their nose.