noun which may take the genitive case particle 'no'
Technical term used in engineering and construction to describe a seal or structure that prevents water from entering or escaping.
This door has a watertight structure.
水密試験を実施した。
We conducted a watertightness test.
watertight door
Compound of 水 (water) and 密 (dense, tight). The combination directly conveys the meaning of being impervious to water.