Gungans are tall Aliens with large floppy ears. Jar-Jar Binks, a Gungan is the most hated character in the Star Wars Universe. The Gungans live entirely on the Planet of Naboo and live mainly in underwater cities led by Boss Nass.
When the Trade Federation blockade the planet, the humans above the water call on the Gungans for help. Before the Trade Federation blockade, Gungans and humans lived separate lives without any interaction between themselves.
The leader of the Gungans is Boss Nass who takes a little convincing before the Gungans agree to help the humans break the blockade of the planet.