Throughout the inshore waters of Japan, from Hokkaido to Okinawa, dwell a bevy of physically sturdy females whose existence is interdependent with that of the ocean. Twice a day, during open season, a high-pitched, reposing breathing sound known as the isobu (sea whistle) is emitted by the labourers between deep dives.

For well over a century, women in the South Korean island province of Jeju have made their living by freediving, ill-equipped, to the depths of the ocean to harvest seaweed and shellfish.

“What lies at the depths of the ocean?” A question that many scientists have been asking for centuries, and still ask to this day. To attempt an answer to this question a number of deep-sea expeditions have been launched to better understand this deep, dark alien world… We bring you six of the most influential.