These two node setups were developed by me with the help of some guys on BA (see thread here: http://blenderartists.org/forum/showthread.php?278101-Look-into-the-water-Shader-Recreation). Both shader try to fake the light absorption and blurryness of water relative to the depth. In difference to the popular light absorption shader the object doesnt need a thickness and thus can be perfectly been used in combination with the ocean modifier. Remember that these shader are very fake and might have their pro and cons.
Please also see the completely updated version: http://www.blendswap.com/blends/view/71434