In 1976, humanity was landing spacecraft on Mars and building supercomputers, yet a massive 15-foot alien-looking shark was swimming right under our noses, completely unknown to science. The megamouth shark is one of the most sensational discoveries in 20th-century marine biology, a creature we missed entirely while mapping distant planets.

Accidentally hauled up tangled in a Navy sea anchor off Hawaii, this 1,600-pound filter feeder was so bizarre that scientists created an entirely new taxonomic family for it. This episode reconstructs the megamouth story, from its visceral discovery to the latest genetic tracking that is finally pulling this deep-sea phantom out of the shadows.

• How the sheer scale of the dark, deep ocean kept a minivan-sized predator hidden until 1976
• Why its soft, flabby body and tiny peg-like teeth make it a sluggish swimmer feeding on plankton
• The decades-long lip mystery and the 2020 study that proved it reflects rather than glows
• The daily vertical commute that ties it to the largest migration of biomass on Earth
• The genetic analysis showing the global population is one single interbreeding family