Originally Posted by KLouis

Crete being part of Greece, you don't have to go through customs when "connecting" in ATH. You do, though, have to go through security and immigration as you cross from intra-Schengen to non-Schengen (from either the B or the CI area to the A gates). By the way, everything is under one roof in Athens.

As for the ferry, it is certainly very, very reliable. It leaves Heraklion around 9 pm and arrives at Piraeus around 7 am. Using public transportation (train or bus), you'd be at ATH before 10 am. The question is what would you do till 5 pm, which is why some of us suggested a flight the day before the TATL and overnite in Athens.