National Geographic City Under the Sea

With a host of problems threatening the earth's surface, is underwater
living a viable alternative? Meet the scientists who believe that
permanently submerged colonies are not just possible, but imminent.

National Geographic follows the scientists as they tackle the
hypothetical challenge of housing 100 families below the ocean's
surface and race to overcome obstacles such as bone-crushing
pressures, ravaging storms and scalding volcanic fluids to create
self-sufficient underwater communities