Sounds like you've got the right idea mixing beach time with actual exploration instead of turning into a lobster for two weeks straight. Once you start looking into all the old ruins and castles in that region, you realize there's way more to do than you even have time for. Renting a car gives you the most flexibility to cover ground and hit multiple sites in one day. You can throw all your stuff in the trunk, crank the AC when it gets hot, and not worry about carrying bags around while you're climbing through ancient amphitheaters.