Vouliagmeni is about half an hour from Athens by car and is a great place for beachside dining. I find that this area has amazing views and is much less crowded than Athens. I haven't been to any beaches there, so please let me know if there are good spots to swim nearby. I usually go for dinner if im staying in Athens and then take a taxi back. My favorite spots are Ithaki and Lavros. Check them out!