We did this tour last April. It was a chartered ferry as there were royal ships in port as well. Not sure how they come up with the timing, but I would say not worth it. By the time everyone boards ferry, you land on mainland, have to walk a bit to the tour busses, get everyone off the busses and then you have a decent walk to the entrance of the ruins which some do slower than other and you will be waiting for the slow pokes, they then make a bathroom stop at the tourist shops, etc. By the time you actually get into the ruins, you have barely enough time to take their guided tour and take some photos, then walk back out and pick up lunch to eat on the bus back to Playa del Carmen and catch the ferry. You will NOT have shopping time. I think we had 30 minutes of free time max in Playa del Carmen. So much wasted time.