Water or trees? actually, a rooftop is better than either, there is a good chance you will be noticed and rescued. But a controlled flight at the slowest sustainable airspeed will probably save you if not the aircraft. Without an immersion suit properly zipped up you won't last long in water.
A while ago, a glider parked in treetops near the M40 caused traffic chaos until they had to lift it off with a helicopter....the occupants had to sit quietly in the glider for an hour before the fire department arrived and extracted them; during the hour, the newbie was persuaded to sign up for a week's course....