In the 20th century, oceanographers mainly used two ocean-water samplers to determine the essential physical properties of seawater: Nansen bottles, made of metal with thermometers attached to record the temperature and pressure of the sample site, and electronic temperature profilers, or CTDs—an acronym for conductivity, temperature and depth.
Click here for original story, New approach to correct systematic errors in bottle data of ocean temperature
Source: Phys.org