Charles Darwin in 1840, aged 31
About 40 years before Challenger, in around 1831, the Admiralty re-outfitted one of its ten-gun warships, the Beagle, for a voyage of scientific survey, and organized an expedition to survey Patagonia and Tierra del Fuego and the shores of Chile, Peru, and some of the islands of the Pacific. A young Charles Darwin was the naturalist for the voyage. The Beagle sailed from Devonport, England, December 27, 1831; and, after a cruise of almost five years, she returned to Falmouth, England, October 2, 1836. Her course had lain across the Atlantic to the Brazilian coast, south along the east coast of South America to Tierra del Fuego, and northward along the coasts of Chile and Peru. She then turned west and crossed the Pacific to Australia, sailed the Indian Ocean, and traveled around the Cape of Good Hope, across the South Atlantic and to Brazil, then home to England.
Darwin's observations during this five-year voyage helped form his theory on the origin of species which provided that the deep ocean would be populated with life forms seen on land only as fossils.
But there would be doubters, and those with very differing points of view.