Nansen bottle (left, about 1930) and with support for two reversing thermometers (right, about 1950).

This water sampler was designed to collect samples at selected depths by the Norwegian oceanographer Fridtjof Nansen around 1910. It is made up by a cylinder with a valve at each end, which is immersed in water attached to a cable with valves in an open position. Once the desired depth is reached, a messenger (i.e. a hollow weight running down along the cable) is launched. The messenger reaching the sampler triggers a release mechanism. The upper end of the sampler is released and the cylinder fall downward closing the valves and trapping the water sample inside.