I know a lot of people that are able to keep eyes open underwater in the sea. I can't, so don't ask me how they do it. I start crying even if a drop goes near my eye.
I'm one of them. I dunno about sea specifically, but I live along the gulf which is salt water.
But I can also touch my own eye (which freaks my wife out) without immediately squinting in pain.
Funny thing is, I can't put eye drops in my eyes worth a damn though.. lol.