Here's one that you probably don't think about much.
How does Squidward's clarinet work? On land, you would need to blow air into it.
So how does he make it work underwater?
As you can see here, bubbles come out:


My theory is that his clarinet has some sort of electrolysis thing in it that creates oxygen out of water :p
Edit:
We'll go with my answer on this one where the clarinet is come kind of specially made clarinet for underwater that generates oxygen to make the sound.
How does Squidward's clarinet work? On land, you would need to blow air into it.
So how does he make it work underwater?
As you can see here, bubbles come out:
My theory is that his clarinet has some sort of electrolysis thing in it that creates oxygen out of water :p
Edit:
We'll go with my answer on this one where the clarinet is come kind of specially made clarinet for underwater that generates oxygen to make the sound.