Often described as undersea rainforests, coral reefs are among the most diverse -- and threatened -- of Earth's ecosystems. Rising from the seafloor, reefs do resemble the exotic terrestrial forests they're compared to, except that here, tree trunks are built not from wood but from hardened sodium minerals, breezes arrive in the form of aquatic currents, and fish, not birds, flit through coral branches. Thousands of species depend on these colorful assemblages, including us. Unfortunately, we're doing a pretty good job of harming many of the world's reef forests. More than 60 percent of reefs are under immediate and direct threat (.pdf); without intervention, a huge number of those could vanish within the next 40 years. A recent estimate suggests that 80 percent of the corals in the Caribbean are already gone. Rising sea temperatures, agricultural runoff, increased ocean acidity, invasive species, and interfering with native ecosystems (for example, by killing sharks) jeopardize reef health. It can take as many as 30 million years for some kinds of reefs to grow, and just a fraction of that time to destroy them. (See these maps for the locations of reefs at risk now, in 2030, and 2050.) That's why scientists are so keen to document and map these astonishing aquatic forests. Using special undersea camera equipment, teams from the Catlin Seaview Survey are capturing the world's reefs and rendering the images as 360-degree, interactive panoramas. The images, more than 100,000 so far, are the foundation of the Catlin Global Reef Record -- a database that's accessible by both scientists and the public. So far, the Catlin team has surveyed reefs in the Caribbean, off the coast of Australia, near the Galapagos, and around Hawaii. Last week, they visited the Mediterranean, studying the shoreline off the Monaco. To photograph the reefscapes, scientists use a specially built underwater camera, the SVII (above), that takes 360-degree, high-res images every three seconds. They not only stitch the images into immersive and absurdly beautiful scenes, but use them to produce videos of each reef surveyed. And that's not all the images are used for: Software developed by the Scripps Institution of Oceanography helps scientists take a census of the organisms captured in the photos and calculate reef coverage, on scales from meters to kilometers. We're not sure what the eel image being captured at left will be used for, but we sure wish we could see it! If you're anything like us, viewing these panoramas is going to make you hate sitting at your desk. So be warned. Above: Osprey Reef, Australia A photographer and marine biologist swim with a big grey reef shark (and its sharky friends) in this panorama (interactive below). (Top image: Catlin Seaview Survey. Second image: Scientists survey the coastline in front of the Oceanographic Museum of Monaco. Third image: A moray eel inspects its reflection in the Catlin camera. All images: Catlin Seaview Survey)

Ribbon Reef No. 3, Australia Schooling Spanish Flags swirl around a coral-covered hill that's part of the Ribbon Reef known as "Steve's Bommie." The team surveyed the reef in November 2012. Image: Catlin Seaview Survey

Great Barrier Reef, Australia Philippe Cousteau drives a Catlin Seaview Survey scooter near Wilson Island, in the Great Barrier Reef. The coral in the image is huge, and about 500 years old (the Great Barrier Reef itself is about 20,000 years old). [Interactive panorama] They might look hard and lifeless, but healthy corals are very much alive, comprising colonies of organisms in phylum Cnidaria (which includes anemones, pictured at right sheltering a Nemo-like fish). These soft-bodied critters deposit calcium carbonate (the mineral found in sea shells) beneath and around them, gradually constructing the skeleton of a coral. Images: Catlin Seaview Survey

Galapagos Islands, Ecuador For 10 days in May, Catlin teams were in the Galapagos Islands, best known for Charles Darwin and his finches (perhaps less well known is that Darwin's theory of atoll reef formation, published in 1842, is still considered mostly correct today). The volcanic archipelago, with its complement of marine life, is one of the most biologically diverse places on the planet. Here, sea lions play near the Catlin survey team (this is an especially fun interactive). Image: Catlin Seaview Survey

Wilson Reef, Australia What look like giant, flat mushrooms are corals populating the mounds comprising the exceptionally alien-looking Wilson Reef. This small reef, which lies within the Great Barrier Reef complex, is perhaps best known for its birds. Sooty Terns and goofy-looking Brown Boobies use the reef for nesting, and it has been designated an Important Bird Area by BirdLife International. Though the Catlin team isn't necessarily keeping close track of the many critters that use these reefs above the water, they are looking for the numerous rays, turtles, sharks, eels, and fish that congregate at these undersea oases. And, they've found at least one giant clam (right). It's hard to image a mollusk weighing several hundred pounds, but there you go. Images: Catlin Seaview Survey

Aruba, Caribbean Sea Aruba sits off the Venezuelan coast, a tropical island destination that is the site of many shipwrecks. Here, the Catlin team dives near the SS Antilla, a German cargo ship that sank 73 years ago. Now, the wreck is being colonized by some corals and other marine invertebrates. Unlike neighboring Bonaire and Curacao, Aruba has no designated marine protected areas -- so the team saw many large remnants of coral colonies that were struggling to survive or were already dead. Image: Catlin Seaview Survey

Osprey Reef, Australia Osprey Reef, in the Coral Sea, is a submerged, elliptical atoll with reef walls that rise almost vertically from the seafloor. Atoll reefs form around extinct volcanic islands; as the central volcanic peak sinks, the corals growing around its perimeter remain near sea level, eventually forming a closed ring structure. These are the reefs that can take millions of years to form. At left, a diver asks a turtle to smile for the camera, and is subsequently ignored. Images: Catlin Seaview Survey

Whale Sharks, Mexico Mexico is home to the second-largest natural reef in the world: the Mesoamerican Reef in the Caribbean. It stretches for more than 700 miles from the Honduran Islands to the tip of the Yucatan, near Isla Contoy. It's here, near this Mexican island, that the Catlin team documented their swim with whale sharks. These gentle, filter-feeding giants can grow to be more than 40 feet long and are a popular attraction for snorkelers and divers in Caribbean waters [interactive panorama]. Whale sharks aren't the only large animals the team got to swim with: The Maori Wrasse (also known as a humphead wrasse, right), encountered near Agincourt Reef in Australia, can weigh more than 400 pounds and live for 30 years. Images: Catlin Seaview Survey

Lady Elliot Island, Australia The southernmost of the Great Barrier Reef's coral islands, Lady Elliot is relatively young. Scientists think it emerged above sea level around 1500 B.C., and has continued to grow over the last three millennia, partly by the accumulating hardened bird droppings. Here, Bigeye Trevally swarm over one of the reefs ringing the tiny island; below, an interactive panorama from a different perspective. Image: Catlin Seaview Survey

Deadzone, Bonaire This reef is dead. Now barren, the once colorful and varied reefscape is a sandy patch of rocks instead of a vibrant, undersea oasis. One of the major threats to corals in the Caribbean is bleaching, a process that leaches life and color from the colonial organisms. Bleaching occurs when corals lose tiny, photosynthetic organisms that live inside their cells. These organisms, called zooxanthellae, are responsible for the corals' varying color. External stresses, such as massive algal blooms, warming water temperatures, overfishing and rising sea levels, can trigger zooxanthellae to abandon their corals, which kills them. At right, a diver inspects a massive, bleached fire coral that should be a bright orange. Image: Catlin Seaview Survey/Richard Vevers

Galapagos Islands, Ecuador Resembling a murmuration of starlings, these schools of rabbitfish and angelfish swirl and collide in warm, equatorial waters. These two species are harmless, but stonefish (pictured, right) most definitely are not. First of all, yes there are fish in that photo. We count three (we think) bright, multi-colored lumps snuggled into the comparatively lackluster coral. Secondly, stonefish stings can be fatal to humans. Masters of disguise, stonefish carry a powerful venom in the spines located along their dorsal fins. Images: Catlin Seaview Survey/Jayne Jenkins