Your closest bet for shore snorkeling in the Varadero area is Playa Coral, on the old coastal road, about 3km off the Vía Blanca, halfway between Matanzas and Varadero. You can snorkel solo from the beach, but it's far better (and safer) to enter from the Flora y Fauna Reserve (8am to 5pm), 400m east. Professional Ecotur provide guides to take you out to the reef 150m offshore (40 minutes, CUC$5).
There are a reported 300 species of fish here and visibility is a decent 15m to 20m. Diving is on offer, too (immersion CUC$39), but must be organized beforehand through Barracuda in Varadero.
The flora and fauna reserve also incorporates the Laguna de Maya, 2km inland from Playa Coral, with a couple of trails and some boating activities. Ask about packages in Varadero's hotels. The Flora y Fauna center has a bar and masseuse.
Most of the coast hereabouts is a gray-white coral shelf, but there are beaches just west of Playa Coral.