The principal tool that shipboard scientists use to look for plumes is a set of instruments called a CTD (Conductivity - Temperature - Depth) package. The CTD is prepared on board and towed by the ship.

The CTD package contains sensors that collect temperature and conductivity data. It may also include water-sampling bottles—the dark gray cylinders inside the metal frame in the photo above—so scientists can analyze the water chemistry in a shipboard laboratory. The plume is both warmer and chemically different from the surrounding seawater, and the CTD package allows scientists to look for both chemical and thermal signatures.

When all of the equipment is checked and in place, the package is slowly lowered into the ocean. This requires a lot of teamwork. The captain and crew navigate; the bosun and marine technicians supervise the launch, the operation of the instruments, and the recovery of the package; and researchers and students monitor the data feed from the underwater instruments.