Earth: a watery planet: water covers 70 percent of our planet. And 97 percent of that water is in the oceans. Dive in and explore

More than 25 percent of all marine plants and animals call coral reefs home--including 10 percent of all fish that humans eat. But some scientists estimate 70 percent of the world's coral could be destroyed within 40 years. Some culprits: overfishing, pollution, and Earth's warming climate. If all of Earth's glaciers and ice sheets melted, the sea level could rise 80 meters (263 feet). A rise of just 3 m (10 ft) could submerge a coastal city like New York.

FAR OUT!

Jason-1, a joint satellite mission of NASA/Jet Propulsion Laboratory and the French Space Agency CNES, gets a bird's eye view of the oceans. Launched in December 2001, the 500-kg (1,102-lb) satellite orbits around 1,336 km (830 miles) above Earth. For five years it will study global ocean topography, information that could help scientists better understand ocean circulation and forecast climate change.

TAKE A PLUNGE!

                         Epipelagic (Euphotic) Zone

0 to 200 m               Sunlight penetrates this layer, letting plants
(0 to 656 ft)            perform photosynthesis (converting sunlight
                         into energy) to thrive. The layer is home to
                         microscopic organisms like phytoplankton
                         (plant) and zooplankton (animal). Fish,
                         jellyfish, and marine mammals--like the
                         spotted dolphin--live in this zone.

                         Mesopelagic Zone (Disphotic) Zone

200 to 1,000 m           Also called the twilight zone, extremely dim
(656 to 3,281 ft)        light penetrates. Here, no plants grow. And
                         while many marine animals call this ocean layer
                         home, many of those feed on the more abundant
                         food supply in the zone above. Some residents
                         include the mesopelagic squid, mackerel shark,
                         lanternfish, hatchetfish, octopus, and shrimp.

                         Bathypelagic (Aphotic) Zone

1,000 to 4,000 m         No light penetrates to the midnight zone. But
(3,281 to 13,123 ft)     many creatures are bioluminescent (body
                         produces light through photophores, light-
                         producing organs). Sperm whales can dive from
                         the surface down to this zone. Most species at
                         these depths are black or red in color due to
                         the lack of light (like the red mysid shrimp).
                         And some have no use for eyes. Unusual
                         dwellers: tripod fish and hairy anglerfish.

                         Abyssolpelagic Zone

4,000 to 6,000 m         Abyss comes from the Greek word meaning
(13,123 to 19, 685 ft)   "bottomless." With no light, severely cold
                         water, and intense pressure, most creatures
                         here are invertebrates (lacking a backbone),
                         such as sea cucumbers, brittle stars, and
                         tiny squid. One oddball: the Dumbo octopus.
                         Its flapping ears help the beach ball-size
                         critter to hover over the sea floor in search
                         for food.

                         Hadalpelagic Zone

6,000 to 11,033 m        These extreme depths ar mostly found in deep-
(19,685 to 36,198 ft)    water trenches and canyons. The ocean's
                         deepest point: the Mariana Trench off the
                         coast of Japan. Temperature at this point is
                         barely above freezing, and the pressure is
                         over 8 tons per square inch--as if you were
                         bench pressing 48 jumbo jets. Believe it or
                         not, life exists her.

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