If you are wondering about snorkeling in Gran Canaria, the good news is that there are lots of places to do it. You can either bring your own equipment or buy it when you arrive (good quality stuff from one of the dive centres or cheap stuff from one of the Indian shops behind the beach).
You can snorkel at any of the beaches in the south but Puerto Rico and Amadores are better than Anfi because the sand at Anfi is really powdery and it’s hard to see anything, especially if there are a lot of swimmers in the sea kicking up the sand. Mogan is OK for snorkeling too, as are Tauro, Taurito and Arguineguín.
If you are in Las Palmas, the northern part of Las Canteras beach is protected by a large bar and this means there is a big lagoon with lots of fish in it.
At Arinaga you can snorkel at El Cabrón. There are a couple of entrance points but there is no path to the beach. It’s possible to get to it however (I’ve done it!) and there are some really big fish there. El Cabrón is one of the best scuba diving places in Gran Canaria too.
If you are snorkeling anytime between October and May you might want to bring a short wetsuit. I always use one. Some people find the water temperature OK for snorkeling without one (it’s about 19ºC in the winter and 23ºC in the summer) so maybe I’m just a wimp 😀