When was the first deep-sea fish photographed in its natural habitat?

An iconic early photograph of a deep-sea fish in its natural habitat was taken in 1939, using one of the first deep-ocean camera systems. At a time when most deep-sea creatures were known only from trawls and dead specimens, this was a major advance. Seeing animals alive in the deep ocean helped scientists understand their behavior, posture, and habitat. It also showed that the deep sea contained complex ecosystems rather than just isolated oddities. Underwater photography later became essential for marine biology and ocean exploration.