Thrill-seeking divers get their adrenaline fixes with open-ocean big-animal encounters, and this region certainly delivers electrifying dives. The nutrient-rich waters of the eastern Pacific Ocean teem with mammoth marine life, and the many remote outpost islands are magnets for pelagics. Ecuador’s Galapagos Islands, Costa Rica’s Cocos Island, and Mexico’s Guadalupe Island and Revillagigedo Islands are home to huge schools of hammerhead sharks, massive mantas, filter-feeding whale sharks, sea turtles, mola mola and so much more. And on Mexico's mainland — at dive hot spots such as La Paz and Cabo Pulmo — more thrills await.

SEE ALL: 100 Best Dive Sites

It won’t take longer than a few feet to realize you have descended into a pelagic paradise at Roca Partida. On one side, a sheer wall (that drops to 180 feet) is marked by crevices painted in sponges. On the other, the beautiful blue is filled with such a frenzy of energy you won’t know where to turn. Converging ocean currents keep the surrounding waters productive for a variety of fish and keep the schools of Galapagos sharks, silkies, silvertips and whitetips busy. It’s not uncommon to see hunting sharks on the boils of skipjack tuna. A swim into the blue could yield schools of giant yellowfin tuna or even hammerheads. Seasonal migrators to Roca include pregnant whale sharks as well as nursing humpbacks. Top this off with routine visits from giant Pacific mantas and you have multiple reasons why this site and the surrounding archipelago were named to the UNESCO World Heritage list. — David Valencia

At Cabo Douglas, on the northwest side of Fernandina, a famous Galapagos attraction can be seen: marine iguanas. These endemic iguanas feed almost exclusively on algae that grows on the shallow rocks off the small beach where they live. Before noon, when the sun beats down on the sand, they slip into the sea to cool their bodies, though they can’t stay too long. Like other reptiles, they need to alternate their time between warm and cool spots to regulate their body temperature. — Tobias Friedrich

If you seek face time with the most gregarious and infectiously joyful residents of the sea, the set of rocky islets in Mexico’s Sea of Cortez known as Los Islotes is the place to be. Buckle up and enjoy the thrill ride as you snorkel with the resident colony of California sea lions. Recording all the action is as easy as sticking out your camera while the pups put on a show, nailing loop the loops and darting to and fro, seemingly for your personal entertainment. — Andy Zunz

This tiny volcanic island 165 miles west of Baja California is home to hundreds of recognized great white sharks; some measure a whopping 19 feet long. The visibility can often exceed 100 feet, making it an ideal location for shooting still images and video. Most boats that visit Guadalupe use both surface and submersible cages. The surface cages give nondivers the chance to see these magnificent animals in the wild. Certified divers prefer the submersible cages, which are lowered down to 30 feet, where the sharks tend to congregate. — Todd Winner

About 15 years ago, a local diver and spearfisherman named Mike Rapu decided to honor his grandfather by building and sinking a moai in the middle of Hanga Roa Otai bay off Rapa Nui. More commonly known in the west as Easter Island, Rapa Nui is famed for its architectural sites, including more than 900 moai, monolithic human figures carved by the Rapa Nui people between 1250 and 1500. The stone figures represent deified ancestors. Only a five-minute boat ride from the shop, the 10-foot-tall moai copy lies in 60 feet of water, surrounded by a white sandy bottom and a coral garden. As soon as divers begin to descend, the stunning visibility allows them to immediately distinguish the silhouette of the statue. Moray eels, green turtles and big jacks are only some of the species we encountered while diving the sunken moai, a tribute made by one Rapa Nui man to his grandfather, who taught him all there is to know about the sea. — Eduardo Sorensen

Witness one of nature’s most incredible displays up close, as thousands of bigeye trevally move in perfect unison. Here, in Cabo Pulmo National Park at the southern tip of Baja California, it’s a common sight. This protected area, heralded as an impressive example of marine protection done right, features the northernmost coral reef in the eastern Pacific. At Los Morros, expect to see tantalizing schools of jacks, massive gulf grouper, the occasional sea turtle and maybe even devil rays schooling near the surface. — Andy Zunz

They’re not the brightest bulbs in the ocean firmament — watch closely: The black jack that leads each pack is the real brains of the operation — but the abundant whitetip reef sharks of Isla del Coco have an overriding driving force that makes their feeding frenzies in Manuelita Shallows a reliable sight: They’re hungry. Once a pack of Triaenodon obesus zeroes in on prey, it’s explosive, with the sharks lunging into rock and coral with a ferocity that has you half expecting them to knock themselves out. (They’re actually extracting reef fish, lobsters and crabs inaccessible to other sharks.) They travel in dizzying numbers, zipping around like crazed IndyCar drivers; surge can add to the feeling that you’re on a carnival Tilt-a-Whirl. Feeding frenzies are most common in shallow water at night, but keep your eyes open: It can happen anywhere, anytime. — Mary Frances Emmons