We did the sunset catamaran tour after getting engaged. It is beautiful to be out in the open ocean here and you get to travel to the end of the island to see the flamingos.
There are various companies that offer this in the center of the island. You can swim in the bioluminescent waters in Holbox. It is best when it is cloudy or there is no moon.
We haven't been to this place, but Holbox is also known for kitesurfing for anyone interested in learning or practicing.