Guam’s pristine beaches are one of its most stunning features. However, if you don’t go past the shoreline, you’re missing a whole world that’s just waiting for you to explore. Whether you’re an avid snorkeler, a certified scuba diver, or a landlubber who’s completely new to underwater adventures, we’ll take you on a tour of some of the most interesting creatures you’ll see in Guam’s underwater world.

Given that you’ll find 300+ types of coral and 900+ varieties of fish in Guam’s waters, we can only scratch the surface in terms of what’s out there. However, we hope these 13 creatures will pique your interest in spending more time underwater so you can start your own list of your favorite fish, crustaceans, invertebrates, and more.

Where to Go: Guam's Marine Preserves 

Looking for spots to snorkel or dive around Guam? Start with the island’s protected marine preserves. Fishing is restricted in these areas, so you’ll get to see plenty of fish, coral, and underwater creatures at the following locations:

  • Tumon Bay Preserve (Tumon) – Tumon Bay is a great place for beginners, since there are lifeguards on duty. The sheltered bay is usually calm, with a good variety of fish.
  • Piti Bomb Holes (Piti) – Despite its name, the giant caverns you’ll see in this marine preserve are not bomb holes, but natural formations that shelter a number of different underwater creatures.
  • Sasa Bay Preserve (Piti) – Home to a significant mangrove population, Sasa Bay is also a great spot to see stingrays and turtles.
  • Achang Reef Flat Preserve (Merizo) – You’ll see plenty of hard corals in this preserve. Look carefully in and around these structures to spot fish, nudibranchs, and other reef inhabitants.
  • Pati Point Preserve (Yigo) – Because this preserve lies close to Andersen Air Force Base, only those with base access (or guests of those with base access) can access this preserve.

Now that you’ve got some ideas about where to go, let’s talk about what you might see. 

Green Sea Turtle

Chelonia mydas

Once an endangered species, the population of Guam’s green sea turtle (haggan bedi in Chamorro) has increased by a factor of eight in the last 50 years. Green sea turtles are the most common species you’ll see around Guam, but you may also spot a hawksbill turtle (Eretmochelys imbricate). How can you tell them apart? Hawksbill turtles have a more prominent, sharp beak. Green turtles also tend to keep their shells very clean.

Did You Know? Turtles can travel more than a thousand miles. Several turtles have been tagged on Guam and tracked all the way to the Philippines. 

Black-Tipped Reef Shark

Carcharinus melanopterus

There’s nothing that’ll get your heart pumping quite like the sight of a blacktip reef shark (hålu’u in Chamorro). These sharks were formerly hunted for shark-fin soup. However, regulations passed in Guam in 2010 banned the possession, sale, and distribution of shark parts, protecting the island’s shark population. If you’re nervous about encountering a black-tipped reef shark, don’t be! These sharks are rarely aggressive, and they tend to favor a diet of crustaceans, mollusks, and other invertebrates. (Not humans!)

Did You Know? During feeding frenzies, black tip reef sharks are capable of leaping completely out of the water. Pretty impressive, right?!

By the way, you might also spot the tawny nurse shark (Nebrius ferrugineus) hanging out on the ocean floor while you’re snorkeling or diving around Guam 

Manta Ray
Mobula alfredi

Recent research around Guam’s resident håfula’ population yielded some unexpected results. After 10 years of study, manta ray biologist Julie Hartup counted only 63 rays around Guam, a comparatively small population. Complicating the matter is the fact that Guam’s manta rays seem to be particularly agile at removing their tracking tags. Despite this challenge, what data the scientists were able to gather revealed that juveniles are able to dive to more than 1,300 feet—a depth that surprised the project’s scientists, who suspect that adults can dive even deeper. Research will continue with the goals of protecting Guam’s small but mighty population.

Did You Know? These gentle giants of the sea can grow up to 29 feet in length and to a maximum weight of up to 5,300 pounds.

In the waters around Guam, you’ll also see the smaller—but equally majestic—ocellated eagle ray (Aetobatus ocellatus).

Giant Clam
Tridacna gigas

They might look like something out of a science fiction movie, but Guam’s giant clams (hima in Chamorro) are very real. These fascinating mollusks filter water and feed on the plankton it contains. Hima also hold significant cultural significance for the Chamorro, who have long used the shells to make tools and jewelry.

Although the population of Guam’s giant clams has declined due to overfishing, a new NOAA-funded project aims to cultivate giant clams in Inalåhan and Malesso. This aquaculture venture will provide food, jobs, and shells to continue the cultural practices of the Chamorro.

Did You Know? Although they appear stationary, giant clams can actually move. In their younger years, they’re able to extend a “foot” and use it to shift their location or simply change their orientation. Once they reach maturity, giant clams are often too heavy to do more than rotate.

Octopus cyanea

There are a number of species of gåmson (octopus) in Guam’s waters, the most common of which is the day octopus, Octopus cyanea. These intelligent creatures can be elusive, favoring holes and crevices, where they wait to grab the crabs, clams, snails, and small fish that make up the majority of their diet. Even when they’re out and about on the reef, octopuses are capable of camouflaging themselves by changing colors to match their environment. To spot one, you’ll need to swim slowly and look closely.

Did You Know? Beneath their skin, octopuses have sacs of pigment. They squeeze and contract these sacs to alter the color of their skin and mimic their surroundings. Day octopuses can even change the texture of their skin for the ultimate camouflage.

Sea Urchin
Diadema setosum

Almost everyone who’s spent any significant time in the water has a sea urchin story—an accidental step that resulted in a foot full of spines or a wave that got them speared in the leg.

For the people of Micronesia, sea urchins represent not a snorkeling obstacle but a significant source of food. In fact, excavations of ancient Chamorro sights have unearthed lå’on shells, confirming a long history of sea urchins as food. You’ll find more than 50 types of sea urchins around Guam, including the black long-spined sea urchin (Diadema setosum) pictured above.

Did You Know? Sea urchin skeletons are largely made up of calcium carbonate—the main component in both eggshells and chalk.

Sea Cucumbers
Bohadschia argus

It can be easy to mistake sea cucumbers for a rock or a piece of coral—or to miss them completely. (Especially when they’re covered in sand!) In some parts of Asia and the Pacific, sea cucumbers (or balåti in Chamorro) are considered a delicacy. There are more than 20 species harvested for sale around Guam.

Did You Know? Around 1,250 species of sea cucumbers have been identified around the world. They can range in size from ¾ of an inch to more than six feet!

Reef Fish 

As we mentioned, more than 900 species of fish make their home on the coral reefs surrounding Guam. Since we don’t have room to list all of them here, we picked a few of our favorites. Keep your eyes out for these beauties!  

Amphiprion chrysopterus

Looking for Nemo (and his close relatives)? You’ll find them on Guam, often tucked into the waving tentacles of an anemone. These two organisms have a win-win arrangement in which the clownfish hides within the anemone for protection and food, and, in turn, the clownfish keeps the anemone safe from predators.

Just remember, the stings of an anemone can be fierce for humans, so observe Nemo and his home from a safe distance.

Did You Know? Clownfish are all born male, but they can change sex and become female. That change becomes permanent; they’re never able to change back to male again in their lifetimes.

Spot-Banded Butterflyfish
Chaetodon punctatofasciatus

The spot-banded butterfly fish is a popular one for aquariums—but it’s much more thrilling to see one of these small, but colorful fish flitting among corals in the wild. The spot-banded butterfly fish generally feeds on algae found on the reef, so don’t be surprised if you see one nipping at a coral outcropping. These fish can also be a bit shy, so you may also spot them hiding between rocks or under a shelf.

Did You Know? These fish can also be a bit shy, so you may also spot them hiding between rocks or under a shelf.

Orange-Lined Triggerfish
Balistapus undulates

Their unique body shape and vibrant coloring make triggerfish a delight to encounter on the reef. You’ll find a number of different types of triggerfish off the coast of Guam, including the orange-lined triggerfish pictured above and the lagoon triggerfish, sometimes called the Picassofish for its variety of bright hues.

Did You Know? If you look closely at the photo above, you’ll see two shrimp perched on the body of the fish. Triggerfish often go to what’s called a “cleaning station” where small cleaner shrimp and fish will strip away parasites or food morsels from larger fish—another example of a perfect symbiotic relationship on the reef.

Yellow Tang
Zebrasoma flavescens

Yellow tang are another popular aquarium fish, since they add a bright pop of color to any landscape. These lemon-colored fish prefer to swim in packs with other yellow tang, which provides some protection from predators. They also love to hide in and around coral for similar reasons.

Exploring All of Guam’s Gorgeous Landscapes

Waterfalls, mountain views, beaches, jungles—Guam has it all. But don’t forget to look beneath the surface of Guam’s turquoise waters to find yet another of the island’s unforgettable landscapes. These beautiful and fascinating underwater creatures—among many, many others—are waiting for you just off the island’s coast.

Considering a move to Guam? We’d be happy to help you make a stress-free move to the island, so you have plenty of time for all kinds of adventures on Guam—land and sea. Just reach out to our local experts for a complimentary quote to get started.

Tell us about your move!