Boats departing from Piraeus or Lavrio port. The trip lasts around 2,5 hours but sometimes more because of bad weather. I’ve heard about a fast boat that do the trip in 2 hours but I don’t know for sure.
If you don’t have a car there are some local buses that connect Meriha with some other areas like Loutra or the villages.
Apart from those who work for tourism the locals have their own old customs, go fishing, talking for hours at the local cafes and using some animals for transportation or other jobs like for carry around things. I noticed many horses and donkeys doing their job… poor animals! :)