Legrena is located about 2h of bus/car ride from the centre of Athens on the way the cape Sounion, where Aegeus was waiting for his son Theseus after the battle with Minotaur… 
Well, you probably know the myth and why the sea is actually called Aegean. Now the cape features ruins of the Temple of Poseidon, another father of Theseus (yes, he had two fathers!), so it is a popular tourist spot, especially during sunset.
And if you want to combine sightseeing with beach fun, you should stop over at Legrena. There are several beaches of different size, with different ground, open and secluded.
Closer to the bus stop (Athens-Sounio bus) lies a long sandy beach. When we were there in August, it was almost empty, maybe because Athenians left to the islands and tourists do not know about it… It was easy to find a spot with no one else in the nearest 30 meters, but unfortunately it was not easy to find a spot to enter the sea for swimming. Well, it was fine for wading but too shallow for swimming.
But further offshore the bottom is full of urchins, so it’s quite risky to walk.
Since it was also windy we couldn’t play frisbee or beach bats. However, we had a jump rope by chance, so skipping was practically the only way to stay active 😉
On another occasion in mid-October, on a very hot day, I visited the “official” nudist beach of Legrena.
Actually, again even the non-nudist part was almost empty, with one naked man and another clothed in the shade. This beach is pebbly,
and some of the rocks are light-pink!
As the beach was faced directly to the sun and surrounded by rocks, it got really hot; 
I couldn’t sit anymore and went swimming. I saw several more coves with one or few naked men in each.
At one of the coves there was a partly submerged tunnel with some bright pinkish rocks.
Later I walked to the “official” nudist part of the beach. This time the pathway was full beautiful light-green rocks.
The entrance to the naturist part is announced by a notification (in Greek) on a huge rock.
Another announcement is placed in the middle of the beach.
And if you still don’t get the point or cannot read greek, there are some smaller international notifications, like this rock with an “FKK” sign.
Again, there were some rocks of peculiar shapes and colors, like this dark-green ‘mini-vulcano’.
This place must be certainly interesting for a geologist, I bet there are some naturists among them as well.
you can also do cliff-diving. Does it look high enough?
Active Naturists 