Definitions

1. noun

A person trained to operate underwater vehicles or equipment, especially a deep-diving submersible, and to conduct scientific research or exploration in the ocean.

“The team of hydronauts embarked on a mission to map the unexplored depths of the ocean.”

2. noun

A person who explores the ocean, especially in a scientific or exploratory capacity.

“The hydronaut spent years studying the ocean’s ecosystem and its impact on the environment.”