(すいめん)

すいめん
noun
water surface
See also: 水面(みなも) (literary/poetic reading)
1. water surface, surface of the water
The top layer or surface of a body of water.
A fish came up to the surface of the water.
(かぜ)水面(すいめん)波立(なみだ)っている
The water surface is rippling in the wind.
The moon was reflected on the water surface.

水面(すいめん) refers to the surface of any body of water—lakes, rivers, oceans, pools, etc.

COMMON EXPRESSIONS:

FIGURATIVE USE:
水面下(すいめんか) (below the surface) is often used to describe hidden activities or negotiations happening behind the scenes.