oceanography - the scientific study of the ocean, including the properties and movement of ocean water, the characteristics of the ocean floor, and the organisms that live in the ocean
Some of the most important discoveries in marine biology occurred during the 3-year voyage by the British ship HMS Challenger led by Sir Charles Wyville Thomson (1830-1882) to all the oceans of the world during which thousands of marine specimens were collected and analyzed. This voyage is often referred to as the birth of oceanography. The data collected during this trip filled 50 volumes and served as the basis for the study of marine biology across many disciplines for many years. Deep sea exploration was a benchmark of the Challenger's voyage disproving British explorer Edward Forbes' theory that marine life could not exist below about 550 m or 1,800 feet.
HMS Challenger Painting of Challenger by William Frederick Mitchell
Today, many ships perform oceanographic research.
READING CHECK
List three characteristics of the ocean that oceanographers study.
Oceanographers study the physical characteristics, chemical composition, and life-forms of the ocean.
Sonar
sonar - sound navigation and ranging, a system that uses acoustic signals and returned echoes to determine the location of objects or to communicate
Scientists measure the time that the sound waves take to travel from the transmitter, to the ocean floor, and to the receiver in order to calculate the depth of the ocean floor.
Scientists then use this information to make maps and profiles of the ocean floor.
Image of side-scan sonar and multibeam sonar used for seafloor mapping.
Submersibles
Underwater research vessels, called submersibles, also enable oceanographers to study the ocean depths.
One such submersible is the bathysphere, a spherical diving vessel that remains connected to the research ship for communications and life support.
William Beebe (left) and Otis Barton standing next to a Bathysphere.
The Bathysphere (Greek words βάθος (bathos), "depth" and σφαίρα (sphaira), "sphere") is a spherical deep-sea submersible which was unpowered and lowered into the ocean on a cable, and was used to conduct a series of dives off the coast of Bermuda from 1930 to 1934. The Bathysphere was designed in 1928 and 1929 by the American engineer Otis Barton, to be used by the naturalistWilliam Beebe for studying undersea wildlife. Beebe and Barton conducted dives in the Bathysphere together, marking the first time that a marine biologist observed deep-sea animals in their native environment. Their dives set several consecutive world records for the deepest dive ever performed by a human. The record set by the deepest of these, to a depth of 3,028 feet on August 15, 1934, lasted until it was broken by Barton in 1949.
Another type of piloted submersible is called a bathyscaph, is a self-propelled, free-moving submarine.
The Trieste is a Swiss-designed, Italian-built deep-diving research bathyscaphe ("deep boat") with a crew of two, which reached a record maximum depth of about 10,911 metres (35,797 ft), in the deepest known part of the Earth's oceans, the Challenger Deep, in the Mariana Trench near Guam, on 23 January 1960, crewed by Jacques Piccard (son of the boat's designer Auguste Piccard) and U.S. Navy Lieutenant Don Walshachieving the goal of Project Nekton.
Trieste remains the only manned vessel to have reached the bottom of Challenger Deep. The vessel is on display at the U.S. Navy Museum.
Other modern submersibles are submarine robots.
These robot submersibles are remotely piloted and allow oceanographers to study the ocean depths for long periods of time.
Underwater Research
Submersibles have helped scientists make exciting discoveries about the deep ocean.
During one dive in a submersible, startled oceanographers saw communities of unusual marine life living at depths and temperatures where scientists thought that almost no life could exist.
Many of these life-forms have unusual adaptations that allow them to live in hostile environments.
led by Sir Charles Wyville Thomson 
