Ogunquit Beach and Perkins Cove
If you like the beach I would head to Ogunquit Beach. Long sandy beach and not busy. Part of the beach has an American feel, large people in loud clothing pulling mobile fridge's behind them. The further you walk along it has a French Canadian feel which is more familiar to Europeans.
The water is cold but popular with body boarders.
If you like waterfront, shops etc I would suggest Perkins Cove.
Johnny