I've lived within easy walking distance (<1 mile) of a beach for 14 years. You have picnics, bbqs, swim, walk dogs, sunbathe, etc.
My personal favourite thing to do at the beach is wait until 12-1 am, have a long walk along the beach to somewhere really dark, then sit, close your eyes and listen to the waves. Optional extras: stare at the sky, write, meditate, sleep, wait until sunrise.