Sampling the water column is also important
As part of our cruise activities we collect various physical and chemical data about the water column. An instrument called a CTD (conductivity-temperature-depth) is used to get sound velocity profiles which are used to help make our multibeam sonar data more accurate. In addition to sound velocity, this instrument also measures temperature, depth, salinity, dissolved oxygen, pH, and turbidity from the surface to as near the bottom as we can lower. An example of these data from our last cast is presented in Figure 1. We take these casts about every 6 hours, and on some casts we also take water samples for other measurements.
It usually takes two people to safely deploy the CDT, even in calm seas.