Where is a great, relatively cheap vacation spot on the ocean?

We are trying to plan a vacation but we don’t know where to go. We would love to go somewhere by the beach but can’t afford anything crazy expensive.

Thanks!
Yeah, it is pretty vague. Oops. We are hoping to stay in the US, or maybe Mexico or a Caribbean Island. Nothing too far, like Australia (although I would LOVE to).
We were hoping to road trip it, unless we could find really cheap airfare.