In the 1840s, American naval officer Matthew Fontaine Maury analyzed historical logbooks to identify oceanic wind and current patterns, significantly reducing voyage times without any mechanical invention.
Measuring ocean depth using sonar is complicated by variations in sound speed caused by temperature, pressure, and salinity. A Japanese research team used multiple models to measure the Challenger Deep in the Mariana Trench, finding depths ranging from 10,914 to 10,932 meters, with their preferred estimate at 10,927 meters.