Ahhh, if there is a paradise on earth, I think I've found it.  From the great Arch at Lover's Beach (Playa del Amo) on the Sea of Cortez to the pounding surf of the Pacific Ocean, Cabo San Lucas offers some of the best warm-water snorkeling on the Baja Peninsula.  Take a glass bottom boat ride out to the Arch (pick up one in the Marina) and make sure your snorkel bit is intact prior to landing on the beach.  Cruise by the sea lions basking in the sun on their giant rock, marvel at the size of the pelicans as they gobble up the beautiful colorful fish you will be seeing on your snorkeling venture.  Make sure you take a break from snorkeling to walk around the island; you won't regret it!