Wikipedia
Bottom water
Bottom water is the lowermost water mass in a water body, by its bottom, with distinct characteristics, in terms of physics, chemistry, and ecology.
Usage examples of "bottom water".
In the Atlantic, it is sandwiched between two other currents moving in the opposite direction, currents that have been known for some years as the Antarctic Intermediate Water and the Antarctic Bottom Water.
And even in this fundamental bottom water it was possible to go down still more hundreds of feet through the growing plants and roots, never finding any bottom except a growth too dense to permit further descent.