because he is a sponge and not a fish

ok

Because bros a sponge

Well, for the people who are saying "it's because he's a sponge", the episode "Pressure" has SpongeBob, Mr. Krabs, Squidward, and Patrick go to the surface able to breathe without drying up with the only threat being the seagulls that attack them, so that can't be the only reason. And also, in the "SpongeBob Movie" (2004) Patrick and SpongeBob both spend a majority of their time out of water, and sea stars will dry up and die if out of water for up to five minutes. Interestingly, in the episode "Tea at the Treedome", SpongeBob and Patrick both dry out and almost die without water, so there is really no consistency. I'd say it's just SpongeBob logic... y'know, a fire-underwater-type situation.

Thx for that information

Oh... hehe! You're welcome. I hope I didn't come across as rude or confrontational. I just wanted to share my SpongeBob nerdiness.