1.
below the water surface; underwater
Literally refers to the area beneath the surface of water.
氷山の大部分は水面下にある。
Most of an iceberg is below the water surface.
水面下の温度は一年中ほぼ一定だ。
The temperature below the water surface is nearly constant year-round.
潜水艦は水面下を静かに移動していた。
The submarine was moving quietly below the surface.
2.
behind the scenes; below the surface; covertly
Figuratively describes activities, negotiations, or movements that are hidden from public view.
水面下で交渉が進んでいる。
Negotiations are proceeding behind the scenes.
両国の水面下での接触が明らかになった。
Secret contacts between the two countries came to light.
表向きは平静を保っていたが、水面下では激しい権力闘争が繰り広げられていた。
On the surface they maintained calm, but behind the scenes a fierce power struggle was unfolding.
Composed of 水面 (water surface) + 下 (below). The literal meaning refers to what is physically underwater, while the figurative meaning describes hidden activities—particularly negotiations, deals, or conflicts that are not visible to the public.
COMMON COLLOCATIONS:
- 水面下で交渉する: to negotiate behind the scenes
- 水面下での動き: behind-the-scenes movements
- 水面下で進む: to proceed covertly
- 水面下での接触: secret contacts
SIMILAR WORDS:
- 裏で: behind the scenes — more casual and everyday; 水面下 sounds more formal and is often used in news/political contexts
- 陰で: in secret — implies concealment, sometimes with a negative nuance
USAGE:
The figurative sense is very common in news reporting about politics, diplomacy, and business. It suggests deliberate concealment from the public eye, often with the implication that important things are happening out of sight.