I’ve never taken the trip my self, but for some one not enjoying the sea (-sickness), it might be to many hours on deck? Some basic tips;
1) If Sailers are pigs, greek sailors are apparently in a leauge of theire own. Find some one to travel with (on the boat if you travel alone or just girls) – Greeks respect men…....
2) Ferry boardings are a battle – greek grannies are the worst – but after a while I kinda enjoyed it.
3) disembarking is even better – you’ll normally be “attacked” by people trying to sell you a room; It’s usually OK, but can be overwhelming at first – always say U’ll stay 5-6 day’s even if U’ll only be 1 or 2 (better chances).

Personally I would look for a flight to save time – if you can aford it.

When on Crete I’ll recomments the Samaria canyon walk – get an EARLY bus to avoid walking in que. http://community.webshots.com/album/176145138PnecLW
Best walk ever (and I’m Norwegian!).

Should you choose ferries there are fast options (more expencive): e.g. Italy – greece: http://www.superfast.com/Adriatic/English/index.aspx

Info on crete:
http://www.west-crete.com/travel-transport-to-crete.htm

Planes: e.g.
http://www.expedia.co.uk (I have NO experience with using this service)

Best of luck