Resorts with Snorkeling

I depends on what you consider to be "good". If you haven't been snorkelling before then you would probably enjoy it and think it was good. If, however, you have snorkelled in the Red Sea or on the Great Barrier Reef, then the DR doesn't even come close.

When we have been and stayed in the resort of PLaya Dorada all of the trips for snorkelling or Scuba Diving have been to the resort of Sosua. I can only speak about the North Coast but Sosua is certainly the best that 'I' have been to. The Catamaran trips all go to Sosua as well.
You can go out with a banana and the fish will eat out your hand, the water is comfortably warm, and there is a variety of fish. Yes there will be other places in the world that are better, but i thoroughly enjoy the snorkelling at Sosua when i go to the DR.

I dont know if you have ever tried it but Scuba diving is the way to go! The guys at 'North Coast Divers' (sosua) will help if you are in the North of the DR. Also we used these guys at caribbeanmarine@yahoo.com. Have a good time!

Serious snorkerlers usually become Scuba Divers...I would suggest you take an introduction course into scuba....Many AI resorts have very good dive centers where you can become certified in as little as a few days....Most also have "one day" trials in the pool and even on the reef to see if you want to commit to the course...
If you are just an occasional snorkeler and not interested in learning to Scuba Dive, just about all areas are good..I would suggest Bayahibe and avoid Punta Cana/Bavaro though..