Brilliant turquoise waves that matched the color of the cloudless sky lapped gently against the side of the boat. Looking across the water, I scanned the swells, searching for signs of life below the surface. The sunshine glinting off the peaks of the waves fooled my eye, tricking me into believing I'd spotted the elusive mammal I was seeking.

Suddenly, biologist Caryn Self Sullivan pointed toward the blue water. "Nobody move a muscle," she whispered.

Standing as still as I could in the gently swaying boat, I peered over the side. From beneath the shallow water, just a few meters away, a baby manatee poked its gray nose into the air to take a breath. Everyone froze as we watched the calf swim within a meter of the boat. Its mother was nowhere in sight. "I've never seen one this small on its own," Sullivan told us. "He has no business being alone."

Normally, manatee calves stay with their mothers until they are almost 2 years old. Was the calf's mother farther up the channel that flowed nearby?

The calf's unusual behavior was a mystery to Sullivan, ever though she has been studying manatees in the waters off the Central American country of Belize since 1998. Very little is known about the manatees of the Caribbean Sea, and Sullivan hopes to change that. She mainly works within the Drowned Cayes, a chain of mangrove islands about 11 kilometers (7 miles) east of Belize City. Mangroves are aquatic trees that form large islandlike colonies in shallow waters.

I spent a week last winter assisting Sullivan. My trip to Belize was arranged through the nonprofit Earthwatch Institute. Earthwatch volunteers visit research sites around world to help scientists with their work. During my week in Belize, Sullivan was also assisted by two recent college graduates (one from the United States, the other from Canada) and three volunteers (from England).

MANATEE STRONGHOLD

Our research camp was located on Spanish Lookout Caye, an island at the south end of the Drowned Cayes. The shallow waters and bogues (waterways) around the Cayes are a perfect manatee habitat. Manatees are capable of crossing the deep ocean, but they prefer to spend their time in shallow bays, lagoons, and estuaries near shore.

Manatees are endangered everywhere in the world. Many die each year when they are struck by boats or get tangled in fishing gear. In some parts of the Caribbean Sea, the gentle mammals are hunted for meat. The country of Belize has a long history of wildlife conservation and has had laws protecting the manatee since the 1930s. Because of that commitment to manatee conservation, scientists consider the country to be a stronghold for the troubled species.

CARIBBEAN COUSIN

Each morning, after breakfasting on tropical fruit, tortillas, or freshly baked bread, we coated ourselves with sunscreen, loaded the boat with supplies, and headed out for a day of work. With only a scattering of small clouds in the sky, the sun was strong on the water. A canopy over our small boat provided welcome shade, and frequent dips in the calm sea kept us cool. Under Belize law, we could not get into the water for the purpose of swimming with manatees. Fortunately, manatees are curious creatures, Sullivan told us. They've been known to swim close to unsuspecting snorkelers and look the humans right in the face.

The manatees of Belize are members of a subspecies called the Antillean manatee. They are close relatives of the Florida manatee, a subspecies that inhabits the shallow waters of Florida. Both groups belong to the same species of West Indian. manatee. A good deal of research has been done on the Florida manatee over the past 30 years. Much less is known about the Antillean subspecies.

Sullivan suspects that the behavior of the Antillean manatees differs from that of their Florida cousins because the two groups live in different environments. For example, Florida manatees migrate north along the Atlantic coast each summer, then head back to the warm, shallow channels of south Florida for the winter. The water is warm in the Caribbean year-round, so Antillean manatees don't migrate to stay warm. But do they travel? No one knows.

CURIOUS CREATURES

Every day we anchored our boat in a different area and watched the water for the nose of a manatee coming up for air. Whenever we spotted a manatee, we observed it as long as we could and recorded its behavior. Sullivan wants to gather all the data she can to gain a better understanding of how and where Antillean manatees spend their time.

One day, after scanning an area for nearly 30 minutes, we spotted a manatee a good distance away. We watched it surface to breathe several times, writing down everything we could about its actions. seemed to be moving closer and closer to us. I recorded its distance from the boat each time it surfaced. Suddenly it was right next to the boat. It seemed to be looking at us. Everyone on board stared back, thrilled to be so close to the creature.

As she always does when a manatee doesn't seem too nervous, Sullivan threw on her mask and swim fins and slipped quietly into the water. The Belize government has given Sullivan special permission to study manatees underwater. She swims up to them slowly, filming them with an underwater video camera. She hopes to create a video database that will help her identify individual manatees by their unique features, such as scars, markings, and even the pattern of wrinkles on their noses.

As we watched from the boat, Sullivan videotaped the curious manatee. After a few minutes, it swam away. Sullivan tried to follow but couldn't keep up with it--an animal designed for life underwater. Later. back at camp. Sullivan showed us the video. She pointed out a small, irregular notch in the manatee's tail. She remembered seeing that notch before. Her system of identifying individuals seemed to be working.

REEF VISITS

Sullivan also hopes to learn more about manatee communication. Manatees are solitary creatures that live alone rather than in groups. They rarely vocalize, but mothers and calves do "speak" to one another. When Sullivan spots a mother and calf together, she records their vocalizations with a hydrophone, a device that detects sound underwater. The calls are squeaky, according to Sullivan. They sound like a wet tennis shoe on a linoleum floor," she said.

Another of Sullivan's goals is to solve a mystery on the reef. Her Drowned Cayes research site includes a small section of Belize's coral reef. In the winter months, she has never seen a manatee on the reef. In the summer, she sees them there--but only the males. What are they doing there? Where are the females? She suspects that manatees' peculiar reef behavior has some thing to do with mating behavior.

Solving these puzzles will take Sullivan years of work. To her, it's worth the effort. She's sharing the results of her research with the Belizean government, inhopes that her data will lead to better ways of protecting the manatees.

BACK FROM THE BRINK

I never came face to face with a manatee, but I saw many of the big gray creatures. After a week in a tropical paradise, I left the Drowned Cayes the way I came, cruising across the gentle sea in a small powerboat. There wasn't a cloud in the sky, and the sun was hot on my shoulders.

Soon another team of Earthwatch volunteers would arrive to help Sullivan continue her research. I hope that my work helped in some small way to answer some of the mysteries of the manatee. I hope, too, that the waters of the Drowned Cayes will someday teem with manatees, pulled back from the brink of extinction.

RELATED ARTICLE: Mermaid biology 101.

In ancient times, sailors lonely from being at sea for months often reported catching glimpses of mermaids, mythical creatures with the head of a woman and the tail of a fish. Many people now believe that those "mermaids" were actually manatees. Although manatees may not look much like mermaids, the scientific order to which they belong is called Sirenia, named after mythical female sea creatures called sirens.

The order Sirenia includes four living species: the West Indian manatee, the West African manatee, the Amazonian manatee, and their cousin, the dugong. Although they share a habitat with whales and dolphins, manatees and dugongs are more closely related to elephants and aardvarks.

Sirenians are the world's only marine-mammal herbivores (plant eaters). They feed on sea grass and other vegetation in the warm, shallow waters where they live. Sirenians are large--West Indian manatees can weigh up to 1,400 kilograms (3,000 pounds)--and can eat up to 220 kilograms (100 pounds) of vegetation each day. They maneuver the food into their mouths with large prehensile (grasping) lips. When not eating or traveling through their habitat, they spend time resting on the bottom of the seafloor. Even when resting, they must come up to the surface every three to five minutes to take a breath.

The quickest way to tell a dugong from a manatee is to check out the animal's tail. Dugongs, like dolphins, have V-shaped tails; manatees have rounded paddles that resemble beavers' tails.

A second species of dugong, the Steller's sea cow, is now extinct. Unlike the Sirenians living today, the huge Steller's sea cow inhabited very cold waters. It was about twice as long as an Antillean manatee, reaching lengths of 8 meters (26 feet). Sailors hunted the Steller's sea cow relentlessly, driving it to extinction just 27 years after it was discovered by European explorers in the Bering Sea in 1741.

RELATED ARTICLE: Inside a tropical aquarium.

My expedition to Belize wasn't all work and no play. We also spent time snorkeling above the world's second largest barrier reef, which lies about 3 kilometers (2 miles) east of the Drowned Cayes. A barrier reef is a coral reef that runs parallel to the shoreline. The Belize barrier reef is a habitat to hundreds of unique species of plants and animals.

One day, our Belizean field assistant Gilroy Robinson pointed out a school of brightly colored parrotfish munching on the edge of a large lump of coral. A parrotfish's teeth are fused together to form a beak, which gives the species its name. We could hear the crunching noises the parrotfish made as they scraped algae from the coral. All around us, sea stars, anemones, sea fan corals, and fish of every size and color went about their daily business.

A coral reef isn't just a home to aquatic organisms; it is the skeleton of millions of aquatic organisms. Coral is a cnidarian (ni-DER-ee-en), an invertebrate animal that has tentacles, a saclike internal cavity, and a single opening for taking in food and getting rid of wastes. Jellyfish and sea anemones are also cnidarians. Some species of coral build a hard case of calcium carbonate (CaC[O.sub.3]) around themselves for protection. When the corals die, they leave the cases behind, which accumulate to form reefs.

The reef wasn't the only remarkable underwater habitat in the Drowned Cayes. One day we snorkeled along "the Crack," a fracture in the ground about 4 meters (13 feet) deeper than the surrounding seafloor. The Crack's walls and crevices provided many species with a distinct microhabitat. A microhabitat is a small localized habitat within a larger ecosystem, with conditions just right for a few species.

Sea anemones and tunicates lined the walls of the Crack. A tunicate is a marine animal with a saclike body enclosed in a covering. I also noticed a long-legged crab, just barely visible, peering out through a crevice in the wall.

Farther along the Crack, a wriggling anemone was home to a tiny purple Pederson's cleaner shrimp. This unusual species of shrimp waves its antennae in the water to advertise services as a cleaning station for fish. When a fish pulls in to be serviced, the shrimp removes and eats parasites, dead skin, and leftover food from the fish's skin and gills and even cleans the fish's mouth without fear! The fish don't eat the shrimp because staying clean benefits their health.

Who would have suspected that just a few meters below the water's surface, so many aquatic organisms had taken up such a specialized residence!

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