hi racer,
snorkeling with whale sharks is an experience that I truly recommand as cenote diving. Better do it from Isla Mujeres or Cancun, cause this place are closer than Holbox and the bout ride does not take as much time. they start before 8.....aprox 2 hours one way, you snorkel in groups of 3 and rotate 4-5 times. Its a hard job cause you have to swim hard to follow them.....last year I was lucky to see more than 100 these bigs animals at once. Breath taking.
The same day in afternoon you can move to tulum and the next day you can go diving. Pit is, in my opinion, the best place and I fall in love in cave diving after diving Pit....but it is not the best option for the first dive. Therefore, you need to devote 2 days for cenote diving. Operators that offer diveing in PIT withouth knowing you and how you dive are not worth trying cause they seems not care for safety to much....which is the most important in cavern diving.
I take people diving to cenote almost everyday, together with jeff, we opened tulum scuba which is not a dive center but we work independently, we love diving and teaching diving....no dive center pressure, deadlines and must. we do what we like and have 100 % of satisfied customers. Jeff has been diving here since 97 and he knows every single hole flooded with water in this area.
let me know if you are interested in getting in touch with us. we will make a nice cenote tour including PIT on the second day if you are experienced enough.
I enclose pic form the PIT just to enhance you, but probably its fame is already workd spreaded.....
gosia