For beach riding, a fat bike would be tops. Can't say what ocean salt would do, but I do know that road salt can definitely take its toll on aluminum, too. A lot depends of the aluminum alloy used and its finish. For sure, in the winter in Chicago, had to clean off my bikes after every ride. Both the aluminum and steel frames held up pretty well as long as I did that. It was some of the small parts that took the hit with the salt because it was harder to clean in the small areas where the salt would collect. As for carbon, have no experience with how it reacts with salt. Not being metal, it might not be as sensitive to salt. Maybe we can get some feedback on this.