How do you dive?

Steven gives it to you in Mossdeep City. You can use it in the field after you get the mind badge.

you swim out to the spot where sootpolis is and you dive under water and go around that area until you see a spot with like a cave door and you go in. then you dive up and surf the water until you...

Well, just talk to Lombre then go to Wishcash and let him blab then you get a Dive!!! If you lose it... you're outta luck... that's what I did..... Ugh....

i dont know if i would consider it a dive. But i guess you could say that it is the easiest.

yesbut is slang for a pencile dive...