General:
* Bathymetry: The measurement of the depth of water bodies.
* Bathybiont: An organism that lives in the deep sea.
* Bathypelagic: Relating to the deep ocean zone.
* Bathythermograph: An instrument used to measure water temperature at different depths.
* Bathygraphic: Relating to the depiction of underwater terrain.
Specific:
* Bathycolpus: A deep furrow or groove.
* Bathymeter: A device used to measure depth.
* Bathypore: A deep pit or cavity.
* Bathytroph: A deep-sea fish that feeds on organic matter falling from the surface.
These are just a few examples, and many other words related to depth or underwater environments use the root "bathy-."