Definition - What does Hydroscopy mean?
Hydroscopy is the practice of viewing objects underwater. Hydroscopy uses an instrument known as a hydroscope, which is typically constructed out of a tube with a transparent material (e.g., glass, plastic) inserted into it that allows for observation.
Hydroscopy has many uses. It is often used for scientific discovery of new underwater plant and animal species and to exam the behavior of aquatic organisms. Hydroscopy is used to view underwater pipelines and ship hulls to look for the presence of corrosion. Hydroscopy is also used to survey the floor of a body of water.
Corrosionpedia explains Hydroscopy
It is very difficult for the human eye to see underwater without a hydroscope. When the eyelids are open, water floods onto the surface of the eyeball and distorts the light coming into the pupil. The hydroscope prevents this from happening by using a transparent material that allows light to be received by the eye but prevents the water from contacting the eye. The tube is used to put distance between the eye and the transparent material. The transparent material can also provide magnification if the application requires it.