How do you fish in Pokemon Emerald?
What you to do first is register your best fishing pole (so that
you don't have to take it out a lot) and after the little dots stop
and it says that "I felt a bite!" or something like that you want
to press A as quick as you can and it will keep on doing that but
it will say "A pokemons on the hook!" press A one more time and you
will be in a regular wild Pokemon battle. (You can fish while on a
Pokemon surfing or just o the shore.)