an optical device for viewing objects below the surface of water.

What is the meaning of Hydroscope?

: a device for enabling a person to see an object at a considerable distance below the surface of water by means of a series of mirrors enclosed in a steel tube — compare water glass.

Who invented the Hydroscope?

The original hydrometer, or hydroscope, was invented by Hypatia of Alexandria, a fourth-century Greek scholar and scientist-philosopher.