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!
Year after year, Athens is hitting record highs for temperature. This year, it's getting so hot that we're seeing wildfires again. I highly recommend that if you're visiting the city, that you wear a lot of sunscreen and stay very hydrated. Heatstroke and sun disease are actually very common in Greece, and can be very dangerous. Make sure that you're in the shade, and stopping in restaurants and shops that have air conditioning.