Icefin the robot is designed to go where no human can, swimming off the coast of Antarctica under 2,000 feet of ice. Lowered through a borehole drilled with hot water, the torpedo-shaped machine takes readings and—most strikingly—video of Thwaites Glacier’s vulnerable underbelly. This Florida-sized chunk of ice is also known as the Doomsday Glacier, and for good reason: It’s rapidly deteriorating, and if it collapses, global sea levels could rise over a foot. It could also tug on surrounding glaciers as it dies, which would add another 10 feet to rising seas.