SCUBA DIVING IS UNLIKE any other experience in the world. I earned my certification when I was 14 and shortly thereafter went on my first diving adventure off the coast of Santa Catalina Island, about 65 kilometers (40 miles) south of Los Angeles. My first dive that day provided ample evidence that the ocean is a marvelously strange place. But even more impressive was diving in the Pacific later that night, an experience that blended awe for the wonders of nature with psychological stress from being engulfed in darkness. After all, in the ocean, we humans are not the top predator.

The first time I rolled off a boat at night and sank into the dark sea, I had to fight back panic. The beam of my flashlight penetrated only a few meters ahead in the water, producing an eerie and disturbing awareness of the darkness around me. But soon, being totally enveloped in the cool, velvety blanket of seawater became oddly comforting, even inviting to me. So I broke the first rule of scuba safety and separated myself from my fellow divers by about 30 meters. Then, summoning all my courage, I turned off my flashlight.

Suddenly, I felt as though I had been cast to the dark side of the moon. Fighting to steady my breath, I could sense only the sounds of my regulator and the gentle undulating surge of the current as waves crested above me. Once I calmed down, my body seemed to melt into the inky water. A few minutes later my eyes adapted, and I realized that the blackness was not absolute after all. No longer blinded by the glare of my flashlight, I could see that the waves high overhead were faintly afire with the glow of the moon. Then something large swam by, stimulating a colony of bioluminescent bacteria and kicking up a dim trail of light in its wake. Although I had no idea what kind of creature it was, I was oddly confident that it wasn't interested in eating me. Instead it ensnared me with a luminous lasso as it circled once and swam off.

Eventually I rejoined my diving companions and later learned that they had never missed me. They had been too busy shining their flashlights on the bottom and coaxing curious lobsters from their dens to take much notice of my temporary absence. I probably shouldn't have risked drifting so far from them, even for a short while. Still, the magic of those few minutes has stuck with me for nearly a quarter of a century.

Every diver has had similarly moving experiences. In fact, I am sure that many of the people who read this column share my passion for both science and the underwater world. That is why, in this International Year of the Ocean, I'm delighted to report that marine biologists all over the world have finally recognized that sport divers can be powerful allies. Exciting new investigations are coming to life that could not be carried out without the help of amateurs.

Reef Check is one of the most ambitious of this new brand of endeavor. In a single year this program has become one of the largest international collaborations of marine researchers ever organized. Run from the Hong Kong University of Science and Technology, Reef Check coordinates 100 teams of volunteers who last year surveyed more than 300 coral reefs in the territorial waters of 31 countries scattered throughout the world. These teams are led by professional marine biologists who teach volunteer divers the techniques they need to make a thorough assessment of the health of coral reefs--hot spots of biodiversity that are second only to tropical rain forests.

Before Reef Check began operations last year, no one had mounted systematic surveys of these vital ecosystems on such a broad scale. So the news was disturbing when Reef Check's first overview turned up plenty of evidence of damage being done to these fragile structures. Continuing work should provide detailed pictures of how these habitats are changing and whether efforts to protect them are working. To get involved, consult Reef Check's site at www.ust.hk/~webrc/ReefCheck/reef.html on the World Wide Web.

A second organization that now routinely enlists amateurs is the Reef Environmental Education Foundation (REEF). REEF, which has more than 10,000 members, is headquartered in Key Largo, Fla. (telephone: 305-451-0312, or www.reef.org on the Web). But don't confuse REEF with Reef Check. Reef Check focuses on coral-based ecosystems, whereas REEF surveys fish populations in various places, whether coral is present or not.

REEF assembles teams of professional and amateur scientists and sends them to do biological surveys all over the Caribbean, Florida, the Gulf of Mexico and the California coast. Beginning this summer, REEF will include groups working near the coasts of Oregon, Washington State and British Columbia. Shortly thereafter REEF will extend its reach to include North Carolina as well. Membership is free, but participation in the surveys could set you back a bit. Scuba divers and snorkelers pay fees ranging between $600 and $1,700 to spend their vacations working with world-class marine biologists.

To learn how to identify the species they will most likely encounter, volunteers attend an informal "fish school" in tandem with their scientific missions. REEF also provides these participants with special fish identification cards to carry on their dives. All the information they record goes into an ever-growing database of fish sightings. But you don't have to join one of these organized expeditions to contribute. A small army of divers now take REEF's species identification cards with them whenever they poke about the bottom. (Contact REEF to obtain a fish ID card for a modest fee.) Largely as a result of their efforts, REEF's database--which now exceeds 13,000 entries--is one of the most comprehensive sets of observations about fish populations ever assembled.

REEF volunteers also help to protect fragile marine habitats in other ways. For instance, on a recent trip to Dry Tortugas, off the coast of southern Florida, REEF volunteers found an area that held a surprisingly rich array of coral down to around 40 meters (131 feet) below the surface: large star, pillar, plate and brain coral form a living carpet that covers half the seafloor there. This expanse of nooks and recesses provides an extraordinary habitat for wildlife. Its discovery by volunteers prompted the National Marine Fisheries Service to ban ships from dropping anchor in the area (which would damage the bottom) and to mount their own surveys of this previously unknown patch of deep coral.

Several REEF-trained volunteers have gone on to make other important discoveries. For instance, the Yellow Garden Eel was once known to biologists only because tattered specimens had been dredged up from the Gulf of Mexico decades ago. Then, in 1996, REEF member Ken Marks spotted the yellowish eels in a popular dive spot off Florida's Deerfield Beach. When his photographs of the curious creatures reached the Smithsonian Institution, experts there confirmed Marks's suspicion that he had recorded the first image of this elusive eel in the wild. Amateurs such as Marks have had little difficulty convincing professional marine biologists of their value.

Even the federal government has finally wised up to the potential of amateur scientists. Since 1994 the National Oceanic and Atmospheric Administration (NOAA) has promoted the Great American Fish Count (GAFC), a yearly survey of marine fish. During the first two weeks of July, snorkelers and divers record a snapshot of ocean life. Just as with the Audubon Society's annual Christmas bird count [see "The Joys of Armchair Ornithology," The Amateur Scientist, April 1997], biologists can now study how wild populations are changing from year to year.

NOAA concentrates its volunteers in the national marine sanctuaries located near the Channel Islands off the southern California coast; Monterey Bay off the coast of Monterey, Calif.; the Flower Garden National Marine Sanctuary southeast of Galveston, Tex.; and the Florida Keys National Marine Sanctuary. To get involved, check out the GAFC Web site at www.fishcount.org or call Christy Pattengill at 800-862-3260. Your efforts may help keep the ocean the dazzling natural wonderland I found it to be when I first learned to dive.

For more information about this and other projects for amateurs, visit the Forum section of the Society for Amateur Scientists . You may also write the society at 5600, Post Road, #114-341, East Greenwich, RI 02818, or call 1-401-823-7800.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.