In this thread ---->
http://www.scubaboard.com/showthread.php?s=&threadid=16068&highlight=playa+del+carmen+ferry+cancun , you'll find something like this (updated below):
"1. Flying from Cancun to Cozumel: approximately 20 minutes flying time.
Aerocaribe and Aerocozumel with Mexicana Airlines flies directly from the Cancun (domestic airport) to Cozumel. Current cost one-way is $60 US, cheaper r/t. You can book directly online or with your travel agent. Schedules and fares are available online:
http://www.aerocaribe.com .
2. OR take a "collectivo"/minivan direct from Cancun airport to Playa Del Carmen (approximately 45 minutes traveling time), then ferry to Cozumel (approximately 40 minutes total traveling time). Current cost is ~$16 US per person.
After baggage pick-up, as you walk towards the exit, there will be booths for transportation and taxis. At the booth, ask for a collectivo to Playa Del Carmen. You pay at the booth, receive a ticket and then proceed outside to where the minivans are. They will take your ticket and load your luggage. As soon as one van is filled, the van departs. The vans are readily available all day long.
3. OR express bus from Cancun Airport or downtowm Coz bus station to Playa Del Carmen Bus Terminal (traveling time is the same as in #2)
As soon as you pass immigration (green/red button) just after the transportation pavillions and just before the outdoors, there is a stand that says Express Bus to Playa Del Carmen. ~$15 US r/t pp. Purchase a ticket and there will be Greyhound-like buses outside. They are scheduled:
From Cancun
10:30am 11:30am 12:30pm 1:30pm 2:30pm 4:30pm 5:30pm 6:30pm 7:30pm 8:30pm 9:30pm
From Playa Del Carmen
7:00am 8:00am 9:00am 10:30am 11:45am 1:00pm 3:00pm 4:00pm 5:00pm 6:15pm 7:30pm
Playa Del Carmen to Cozumel (40-45 minutes traveling time)
4. OR take a Suburban. About $60 each way, divided by the number of passengers. Holds about 5 people unless you want it to yourself. About 35-40 minutes to Playe del Carmen.
5. Then from Playa Del Carmen take the ferry to Coz. Ride is about 40 minutes on the large jet boats and about 50 minutes on the smaller, occasional local ferry. Cost is the same for tourists. It docks right at the heart of the city, San Miguel in Cozumel. Current cost is ~$US18 r/t pp. Foot traffic only. Car ferry leaves from Puerto Morelos north of Playa del Carmen.
Daily Ferry Schedule (Central Standard Time) (changes occasionally, but this is the generel plan)
Coz to Playa Del Carmen: 5 am 7 am 8 am 9 am 10 am 12 pm 2 pm 4 pm 5 pm 6 pm 8 pm 10pm 11 pm 12 pm 1 am
Playa Del Carmen to Coz: 6am 8am 9 am 10 am 11 am 12pm 1 pm 3 pm 5 pm 6 pm 7 pm 9 pm 11 pm 12 pm
Obviously no need for a hotel in Playa del Carmen.
Helpful?
DocVikingo