Now is a great time to use some of the handy tools people have made easily available for questions like this. in fact, they are stickied at the top of the forums, where anyone can see them easily. just so you can look there. they're called the strategy index and the Dom3 wiki. there you can find wonderful things like guides to every water nation in the game, including LA atlantis (i recomend the guide written by Baalz)
Edit: i guess the wiki requires a google search, its not stickied yet
http://dom3.servegame.com/wiki/