Have you tried following this tutorial at all? This has been used in maps and it works perfectly fine. Make sure you follow everything correctly.
(http://i155.photobucket.com/albums/s308/ringoluver/customwatertut1.png)
(http://i155.photobucket.com/albums/s308/ringoluver/customwatertut2.png)
(http://i155.photobucket.com/albums/s308/ringoluver/customwatertut3.png)
(http://i155.photobucket.com/albums/s308/ringoluver/customwatertut4.png)
Feel free to post here or PM me if you have any further questions :3