You can fly into Cozumel using one of the many airlines that fly directly or fly to Cancun and then either fly or take the bus-ferry to the island
You can either take a 15 minute flight via Mayair or take the airport vans or bus to Playa del Carmen. (Time: 50 min)
You can take the bus to Playa del Carmen from the main bus terminal (Time: 1 hr)
You must take a ferry ride, ferry runs from around 7am till 11pm. Check schedules upon arrival to Playa del Carmen. (Time: 45 min)