I find that the salt in the air and the wind at the beach mucks up my hair anyways. I wouldn't advise spending too much time on your hair before you go to the beach, especally if you're going swimming.. the water will was out all the hair products out and the effort you spent curling/straightening your hair will be wasted.
don't spend too much time on your hair when you're going to the beach. leave it down and that's it.
yeah like LilLana said, don't worry to much about it. When you jump in the ocean, your hair gets all wet and then it'll naturally dry anyways. usually for me, when I go with straight hair, I jump in the ocean and come out with naturally wavy hair (the salty water does that for my hair)