I've read (for the moment I don't have the reference) that statistics show that the survivability of light aircraft ditchings is quite good.
In fact so good that if you have to make an emergency landing in wooded terrain with little open ground but many lakes (such as you commonly find in Scandinavia), you should ditch the aircraft in a lake rather than take it down into the trees.
Surviving after a successful ditching at sea is of course a different matter entirely...