Mumble is told to leave the community after leading a tap-dancing revolution. His old man supports the elders, and tells everyone that he dropped the egg.
With his little Argentinian penguin friends, they go to Lovelace to ask for directions to find 'the aliens', so Mumble can save the day and bring the fish back.
They find Lovelace choking on the plastic beer wrap, so bring him with. They head towards the ocean, escape from a few evil killer whales (they show that thing they do in wildlife programmes where they menacingly play with the penguins which is the one thing in nature I absolutely hate and shouldn't really feature in a kids animated movie), Lovelace loses his necklace, and finally Mumble braves it alone and dives into the ocean and swims.
He ends up on a beach, and is picked up by a patrol buggy. He wakes up in 'penguin heaven' which is really just a zoo. He starts to go a little loopy, but impresses the American-looking White Caucasian people watching (he must have swum quite a distance from the south pole!!) with his tap dancing. Instantly he is a hero.
Without any warning, Mumble strolls back into the Emperor Penguin colony, and no one has moved much from their original positions. He shows them his radio-tracking device. He patches things up with his remorseful dad, but the elders still want him out.
A team of scientists show up, so following Mumble's lead half the penguins do a dance while the rest sing. Finally they all dance, and the elders suddenly seem to forgive him and join in the dance too.
The scientists assume the penguins are trying to tell them a message. Its covered in the news, and people all over the world agree not to overfish near the Antartic.
The fish soon return, and Mumble gets the girl.