As I mentioned in a previous thread of yours, I used to live in Lebanon.
If you want a real beach (not a lake beach) the closest you'll get is Wells by way of Rte. 109.
Take 202 into Sanford, bang a right on Main Street (109) and keep driving until you see the ocean! Kennebunk will be to your north, Wells, Ogunquit and York will be to your south.
Ofcourse you could also take 109 to Rte. 4 into Berwick, and into York Beach that way, but I think the other way is easier for someone who doesn't know the roads there.
Have fun!