Scientific ocean exploration began in the 19th century, using wooden sailing ships. At that time, explorers had none of the technological sophistication and tools available today. A comparison of modern-day exploration with the late 19-century journey of the HMS Challenger illustrates the progress that science has made in ocean exploration.
Ocean depths were measured with weighted lines until the 1920s, when echo sounders became common. The Challenger expedition utilized a dredge and a grab sampler for bottom samples. The newly invented Nansen bottle was used on the Challenger to collect water samples from different depths.
;