“What lies at the depths of the ocean?” A question that scientists have been asking for centuries, and still ask to this day. In the deadly clutch of the ocean’s dark abyss, what luckless creatures are cursed with never seeing the light of day? To attempt an answer to these questions, a number of deep-sea expeditions have been launched to better understand this deep, dark, alien world… We bring you six of the most influential:

1521 – Ferdinand Magellan attempts to measure the depths of the Pacific ocean

Dropping a penny down a wishing well and waiting to hear it strike the bottom, if you can do the math, is a credible method to calculate the well’s depth. In a similar fashion, to calculate the depth of the Pacific ocean, Portuguese explorer Ferdinand Magellan tried to measure the depth by dropping a cannonball-weighted line, but did not find the bottom. This process, called sounding, meant a ship’s crew would throw out weighted, measured amounts of line, called sounding line. As the line sank, the crew would record the measurement of the line’s length and how far it dropped. After lowering the cannonball 732 metres without hitting the bottom, Magellan declared the Pacific as immeasurably deep.

1850 – Near the Lofoten, Michael Sars’ dredging expedition

Michael Sars, a Norwegian theologian and biologist, set out in 1850 to dredge a part of the ocean near the Lofoten, an archipelago in Norway. Eight years before the expedition, the British zoologist Edward Forbes had issued a series of articles on biogeography, claiming that no animal life could exist at depths greater than 550 metres. As a result of one of Sars’ dredging expeditions, he disproved this theory by pulling up a live stalked crinoid (sea lilies and feather stars) from a depth of 800 metres. This spurred academic interest in the deep sea and prompted the Challenger expedition (see below) and other similar ventures around the globe.

1872-76 – Challenger Expedition

The Challenger expedition was a grand tour of the world covering over 100,000 kilometres organised by the Royal Society in collaboration with the University of Edinburgh. Charles Thomson was the leader of the large scientific team.

To enable HMS Challenger to probe the depths, all but two of the Challenger‘s guns had been removed and the spars reduced to make more space available. Laboratories, extra cabins and a special dredging platform were installed. The ship was then loaded with specimen jars, alcohol for preservation of samples, microscopes and chemical apparatus, trawls and dredges, thermometers and water sampling bottles, sounding leads and devices to collect sediment from the sea bed, and great lengths of rope with which to suspend the equipment into the ocean depths. The Challenger‘s crew was the first to sound the deepest part of the ocean, thereafter named the Challenger Deep.

1930 – Bathysphere

William Beebe and Otis Barton conducted their first test of the bathysphere in 1930, documenting deep-sea animals which had never before been seen in their native habitats. During these dives, they became the first people to observe how as one descends into the depths of the ocean, some frequencies of sunlight disappear before others, so that below a certain depth the only colours that remain are violet and blue. They reached a depth of 435 metres, where they observed jellyfish and shrimp in their natural habitat. The vessel would later go on to reach a depth of 923 metres in 1934.

1960 – Bathyscaphe Trieste

The Trieste, a deep-diving research bathyscaphe, descended to the deepest known part of the Earth’s ocean, the Challenger Deep – at the southern end of the Mariana Trench, in the Pacific Ocean. Jacques Piccard and Don Walsh became the first people to reach the near-bottom of the Mariana Trench, reaching 10,916 metres. The descent took just under five hours, and when at the bottom, they claimed to see fish swimming and recorded the seabed to consist of “diatomaceous ooze”.

2012 – Deepsea Challenger

James Cameron succeeded in tackling one of the Earth’s most testing challenges – reaching the bottom of the Mariana Trench – and he was the first to do it solo. In order to make this journey to the Challenger Deep, Cameron and his engineering team utilised revolutionary engineering and cutting-edge technology. The dive revealed many weird deep-sea species, one of the stranger finds being a sea cucumber believed to be a never-before-seen species. The research also revealed a previously unknown type of squidworm that is several inches long and lives in mid-water above the seabed. The endeavour has inspired many expeditions since.

By Leslie Leaney, this article featured in SD OCEAN PLANET (Issue 4/2015)

Dr. Sylvia Earle is one of the most influential figures in the world’s oceans, with a career stretching back several decades. She was a close personal friend of Professor Hans Hass and enjoyed a professional relationship with several other recipients of the Hans Hass Fifty Fathoms Award.

As an Advisory Board member of HDS USA and HDS Asia, and an inductee into the International Scuba Diving Hall of Fame, Dr. Earle has been connected to the Hans Hass Fifty Fathoms Award founder and Executive Director, Leslie Leaney for several decades. She worked with Award Chairman Krov Menuhin during the development of the Deep Rover submersible programme. Dr. Earle is the recipient of the 2010 Hans Hass Fifty Fathoms Award, which, due to her hectic schedule, was finally presented to her at the HDS USA 2012 Conference in Santa Barbara, California, by the Award’s first recipient Ernie Brooks, and HDS USA Chairman Dan Orr.

Dr. Earle is National Geographic Society Explorer in Residence, and called “Her Deepness” by the New Yorker and the New York Times, “Living Legend” by the Library of Congress, and first “Hero for the Planet” by Time Magazine. She is an oceanographer, explorer, author and lecturer with experience as a field research scientist, government official, and director for corporate and non-profit organizations including the Kerr McGee Corporation, Dresser Industries, Oryx Energy, the Aspen Institute, the Conservation Fund, American Rivers, Mote Marine Laboratory, Duke University Marine Laboratory, Rutgers Institute for Marine Science, the Woods Hole Oceanographic Institution, National Marine Sanctuary Foundation, and Ocean Futures.

Formerly Chief Scientist of NOAA, Dr. Earle is Founder of Deep Ocean Exploration and Research, Inc. (DOER), Founder of the Sylvia Earle Alliance (S.E.A.)/Mission Blue, Chair of the Advisory Council of the Harte Research Institute, inspiration for the Ocean in Google Earth, leader of the NGS Sustainable Seas Expeditions, and the subject of the 2014 Netflix film, Mission Blue. She has a B.S. degree from Florida State University, M.S. and Ph.D. from Duke University, 27 honorary degrees and has authored more than 200 scientific, technical and popular publications including 13 books (most recently Blue Hope in 2014), lectured in more than 90 countries, and appeared in hundreds of radio and television productions.

She has led more than 100 expeditions and logged more than 7,000 hours underwater including leading the first team of women aquanauts during the Tektite Project in 1970, participating in 10 saturation dives, most recently in July 2012, and setting a record for solo diving in 1,000 metres depth. Her research concerns marine ecosystems with special reference to exploration, conservation and the development and use of new technologies for access and effective operations in the deep sea and other remote environments.

Her special focus is on developing a global network of areas in the Ocean, “Hope Spots,” to safeguard the living systems that provide the underpinnings of global processes, from maintaining biodiversity and yielding basic life support services to providing stability and resiliency in response to accelerating climate change.

Her more than 100 national and international honours include the 2013 National Geographic Hubbard Medal, 2011 Royal Geographical Society Patron’s Medal, 2011 Medal of Honor from the Dominican Republic, 2009 TED Prize, Netherlands Order of the Golden Ark, Australia’s International Banksia Award, Italy’s Artiglio Award, the International Seakeepers Award, the International Women’s Forum, the National Women’s Hall of Fame, UNEP 2014 Champion of the Earth, 2014 Glamour Woman of the Year, Academy of Achievement, Los Angeles Times Woman of the Year, UN Global 500, and medals from the Explorers Club, the Philadelphia Academy of Sciences, Lindbergh Foundation, National Wildlife Federation, Sigma Xi, Barnard College, and the Society of Women Geographers.