how can I make realistic water?

I am attempting a new piece and have never worked with still water. Almost like like a lake I want it to reflect but also to maintain visibly the objects below the water line but perhaps a bit blurry with greater depth.

Water has vexed me from the beginning…any advise? I like using yafaray but it is not necessary.

have a look at COG tut for water
or you could do some fluid simualtion for a realist lookand effect