The ferry to Playa del Carmen is about 35 minutes and the ride to Tulum takes an hour, more or less, depending on your mode of transportation and your destination in Tulum (ruins, town, beach). Factor in some waiting time.
Even cruise excursions go there from Cozumel, they're typically scheduled for 7 hrs so definitely doable for a land vacationer.
"Travel changes you. As you move through this life and this world you change things slightly, you leave marks behind, however small. And in return, life — and travel — leaves marks on you.” -Anthony Bourdain
