It can be windy and the current can be quite strong along there and Agia Marina, other times we have been there it has been like a mill pond, nothing moving. Bit tricky if you have children to guage how strong it is.

Apparently, the "Greek winds" can be quite strong and start up quite suddenly. Crete is the island we have been to where it has been extremely windy at times, E.S.N & W. At least it blows the mozzies away.

Yes, this is the famous (not apparently to package tour operators....) meltemi wind which blows in the central and southern Aegean sea, peaks in July/August. This of course affects all open north facing beaches. Even outside of these months it's quite dominant. If you look at a yachting/climate website it will give you the gory details. Crete being so large also means odd currents as has been mentioned.