The difference between ice morphology at the sea surface and under the water is particularly impressive. Though ice is relatively flat at the sea surface, this footage from the ROV shows how ice thickness underwater can change drastically from a few centimeters to more than several meters within a few meters over a very short distance. Because the ROV is connected to the ship via a fiberoptics tether, piloting the ROV underneath the ice is particularly challenging. Not only do the pilots need to monitor the position of the ROV relative to the ice, but they have to always be cognizant of the tether. This string of floats gives the tether neutral buoyancy and prevents it from floating up under the ice. Footage courtesy of Rolf Gradinger, University of Alaska, Fairbanks.