Marietas Islands: Cavern Swim and Snorkel Cruise from Puerto Vallarta. Explore the magnificent marine life of the Mexican Pacific and the Bay of Banderas on an exciting full-day tour from Puerta Vallerta. Snorkel to observe an incredible underwater wonderland; kayak in the warm waters of the Marietas Islands; and watch for exotic birds flying in their natural habitat. Look out for dolphins, whales, giant manta rays and sea turtles as an experienced guide directs your attention to the wonders of nature on this eco-adventure. Book with us and Save 11%: Marietas Islands: Cavern Swim and Snorkel Cruise from Puerto Vallarta.