This is actually a pretty damned good idea. Assuming you mean to go at night, this is a perfect idea. (Day time isn't bad either but the night is the best time for this) Go have dinner and a few drinks then a walk down the beach at night.
Man, I can tell you from experience that a night time stroll down a beach (with or without drinks, but drinks do help though....) is a great idea. It's romantic, and it very often leads to skinny dipping (if you play your cards right). Once you're both naked and enjoying eachother, sex is very likely.