In a C152 with the engine out I think anyone on the ground will be able to get out of the way by walking at a fairly leisurely pace in more or less any direction.
That is assuming they know you are coming and see you. From gliding (sailplane) experience, as you will be coming from downwind, unless its almost flat calm, anyone up wind won't hear you with a stopped engine. I have sometimes wondered whether gliders should be fitted with horns to let people know they are coming!
With regard to hang gliders landing in the water, the wing will hold you under with no airspace in which to breathe. Usual advice is:
- climb into the 'A' frame with plenty of height (they can still be controlled by moving your bodyweight), and undo your carabiner, then just before the glider makes contact with the water, jump clear.
- fly with a single carabiner
- use either a 1/4 turn carabiner or one which just springs shut
- and most importantly, don't fly coastal sites with distant bottom landings in marginal conditions
A friend of mine lost his girlfriend who drowned as a result of a water landing, so they are definitely to be avoided.