scuba diving

The best dive shop IMHO is Pacific Scuba. They have a shop across from (near) the Krystal Hotel. Leslie is an awesome dive master and they are an excellent dive company, small boats with less people per divemaster than some.
They have a website, and email them and ask them if they have the manta ray dive (if it is the season) when you are here- very cool....

for your best rate book on a afternoon cruise to yelapa and tell them you scuba dive before purchasing,chances are you will be the only diver and it will be same place as dive operators go

This might help...

http://www.vallartatraveladvisor.com/dive_sites_map.jpg

Did the Marietas Islands two years ago, nice place to start...

Dive Safe