Does anyone know how to get to pireaus and the ferry docks to either Hydra or aegina from Athens using public transportation ?
You can easily travel to Piraeus by Metro.
My mom and I actually opted to spend a night in Piraeus, before our early morning departure to Santorini, mainly because it was still dark in the morning (early October) when we’d have had to leave our hotel in Athens.
There’s a great central market in Piraeus
where we got delicious fruit, cheese and olives for our picnic lunch on the ferry!
Anyway, here is a very helpful website that explains in detail how to get to Piraeus: Greektravel.com
Enjoy your time in Greece!
Metro, as mentioned before, or bus X95 from Syntagma, or Proastiakos (commuter rail) if you're near a train station). You'll be looking for Gate E8.