Yes there is a lot of diving, scuba, and snorkeling in Puerto Vallarta. There are companies that offer these tours. If you are living in Puerto Vallarta, these water activities would be easy for you to do.
If you want to go snorkeling, you should go through a tour company. It’s not easy to go on your own because you have to take a boat to get to the deeper parts of the ocean or go to beaches that are only accessible by boat.
There are also opportunities to go diving, scuba, and snorkeling in other places around Puerto Vallarta. If you go to the opposite side, coming from the airport, going to the north, there are lots of places where you can do these water activities, such as Nuevo Vallarta, Sayulita, Punta de Mita, etc. All these places are within an hour and a half away from Puerto Vallarta. They are full of expats and some of them have some of the nicest beaches in Mexico. Some of those places are for surfers, some are for snorkeling, and some are just for flat beaches where you could wade and swim.
(Snorkeling at Islas Marietas near Puerto Vallarta, Mexico, pictured.)