Dagobah was the planet that Yoda retreated to after the end of the Clone Wars and the rise of the Empire. He hid there because there was a Dark Jedi that escaped there, and the Dark Side aura shielded his presence there.
In Star Wars: Battlefront II, the swamp of Dagobah becomes a battlefield. There are several command posts, including one in the Dark Side cave. If you listen carefully there, you can hear Darth Vader's breathing.
The water can help you as much as hinder you. One command post is completely surrounded by water, which makes it difficult to shoot enemy units around it. However, if you crouch, they have a much slimmer chance of hitting you. It is the best way to keep that command post and your life.
LEGO Star Wars IIEdit
In LEGO Star Wars II: The Original Trilogy, one of the missions is Dagobah. The player must take Luke through his training with Yoda, all the way from finding Yoda (in his hut, which is contrary to the movies) to fighting Darth Vader in the Dark Side cave and raising his X-wing out of the swamp.