What is called the water mass? What are the main types of water masses?

What is called the water mass? What are the main types of water masses? What water masses are emitted in the surface layer of the ocean?

Water masses are huge volumes of water in the ocean, differing from each other in salt composition, density, amount of oxygen, transparency and the presence of living organisms.
Water masses differ in depth: surface, deep and bottom. The latter are more constant, they are almost not affected by sunlight, the temperature does not change.
The types of surface water masses are named according to geographic zones: arctic, subarctic, antarctic, subantarctic, tropical, subtropical, equatorial.
The surface layer is more variable under the influence of climate, ocean currents, winds and other factors.