Ferry Boats... From North Western Crete.
Crete is the second largest and not quite southern-most island in Greece.  Greece is a major sea-faring nation and has extremely well developed, efficient and regular scheduled ferry boat services connecting all it's islands.  Either directly from Athens, or with scheduled stops at other islands as they ply between their destinations and the mainland.  There are so many ferries that it is possible to spend an entire holiday island-hopping just by booking ferry tickets.  Motor vehicles are no problem and on some ferries, though usually those on the Italian routes,  you can even camp on deck.  The main ferry company serving north-western Crete is ANEK LINES using the port of Souda Bay.  This is supplemented during the summer months by ANEN LINES using the port of Kastelli.

From Souda Bay... Direct to Athens.
ANEK LINES run the daily (overnight) direct service to Athens using the ferry boats Lissos and Lato.  Both boats are really quite large ships.  Every night at 8.30pm each leaves the opposite port, Piraeus or Chania, where it has usually spent the day, bound for the other port.  Passing each other sometime during the night.  These boats are a little different, with Lato being perhaps the more 'sumptuous' - a lounge bar with waiters for example, against a cafe bar with no waiters on Lissos!  Both boats have all modern facilities, including general and classy restaurants, TV lounges and private cabins with facilities - though nobody will mind if you sleep right where you are.  Don't be surprised to find passengers bedding down in public areas - if you don't have a berth you may have to do the same thing.  Remember too that you might be able to book or upgrade your accommodation on the boat, but in the high season don't count on it, book early.  You could actually spend a day (or more) in Athens using these ferries, but it is not recommended near your departure date from Crete as a failed sailing, whilst unusual, could mean missing your flight home. 
Ferry boats, like buses, have schedules.  The boat will leave at the stated time - which is usually visible on a large stationary clock above the loading ramps.  Once the boat commences its departure - even if the ramp has not actually started to lift - it will not stop for a last minute arrival.  It is not that unusual to see cars racing for departing boats, headlights blazing and horns blaring, followed by occupants furiously shouting at deck officers as your ferry gently slips from the quayside!
Loading Time...
Foot passengers board by a special ramp at the side of the vehicle loading bays.  Inside the door you will  find an escalator which takes you to the first deck, where your tickets will be checked, and to reception, where you will find a row of helpful stewards ready to show you to your cabin if you have one and or carry your bags.  A tip is nice - these guys work hard and we all like a thank-you.  They will even let you carry your own bags if you wish, so make your wishes known!  If you have a vehicle you can either let any passengers board separately or take them to the garage decks with you.  It depends on you needs - if you intend to empty your boot, which is completely unnecessary, either arrive early and board separately, or take everyone to the garage to carry the bags.
Drive Aboard.... Safely.
Boarding a Greek ferry is easy and safe.  If you follow instructions.  To the letter.  The crew members responsible for getting you aboard and subsequently disembarking you are highly skilled. They do this almost everyday without serious problems.  The thing to remember is that they board you - often standing by your moving vehicle issuing instructions both verbal and mime.  Boarding ramps are often steep, especially to upper or lower car decks and space is often tight, cars being packed in like sardines and more or less inaccessible once parked.  Being reversed into a space sometimes looks impossible.  Do what the loaders say or indicate - sometimes difficult for the inexperienced and the overconfident.  When the loader tells you to "Look at me!" he means just that - forget your car - let him use you to drive it!  On one trip I was behind a German vehicle on a very tight and confined lower car deck whose driver panicked and refused to comply with instructions.  His wife also panicked, leapt from the car and started shouting that they would leave the boat!  It was very hot; noisy; confined and in the bowels of the boat. The loaders managed to manoeuvre them to one side and then took the smile off the face of the next driver, me, by shouting, one putting a hand on my bonnet, "Look at me!"  I did, I did!
Kastelli - Peloponnese... and offshore islands.
ANEN LINES, an offshoot of ANEK, serves routes to the main islands between North-western Crete and the southern Peloponnese ports of Githio and Kalamata during the summer months.  The car ferry "Myrtidiotissa" sails every day except Fridays and Mondays, but to different destinations on different days often at different times.

Kastelli - Kalamata: Saturdays and Tuesdays leaving Kastelli at 9am; arriving Kalamata on the southern Peloponnese 7pm.
Kastelli - Antikithira: Sundays leaving Kastelli at 11am; arriving Antikithira at 1pm.
Kastelli - Githio: Sunday and Thursdays leaving Kastelli  at 11am; arriving Githio on the southern Peloponnese 6.30pm.
Kastelli - Githio: Wednesdays
leaving Kastelli  at 8am; arriving Githio on the southern Peloponnese 3.30pm
Kastelli - Kithira: Saturday and Tuesdays leaving Kastelli  at 9am; arriving Kithira at 1pm.
Kastelli - Kithira: Sundays and Thursdays leaving Kastelli  at 11am; arriving Kithira at 3pm.
Kastelli - Kithira: Wednesdays leaving Kastelli  at 8am; arriving Kithira at 12 Noon.

Visiting the southern southern Peloponnese is at least the equivalent of visiting Athens, albeit very different.  If you are driving to or from Northern Europe consider this route instead of traveling via Athens if you seek an alternative.  We have friends who swear that it is a better route - including one who arrived via at Souda Bay from Athens and later departed via Kastelli for Kalamata en-route home to the UK.  In an old GPO red post office van!

Safety:  The general safety record of Greek ferries is excellent.  However, two major incidents involving some loss of life in recent years, including the loss of a Minoan ferry, prompted the Greek government to impose stringent safety checks on all ferries - even suspending some until modifications were made.  All Greek ferries are now as safe as any in the world.  I have no hesitation using them - my favourite is the ANEK Lissos!  But only because Minoan retired Festos from their Venice line...