Las Gatas is a short water-taxi ride from the municipal pier in Zihuatanejo — boats run from around 9am to 5pm for a small round-trip fare. The crossing itself is pleasant, with views of the town and the surrounding hills.
The beach is lined with a dozen small restaurants that serve seafood, cold drinks, and rent out snorkeling gear. Snorkeling is best in the morning before afternoon waves stir up the sand. The reef holds sea urchins, damselfish, angelfish, eels, and the occasional sea turtle.
A full day for two — water taxi, snorkeling gear, lunch with fish or shrimp, and cold beer — runs well under $100 USD. Vendors sell silver, shell necklaces, and the odd bottle of homebrewed mezcal, but they're easygoing and not pushy.