Waterproof
Watertight
noun, の adjective, verbal noun
Something that prevents water is waterproof and watertight. Time to take a bath with my 防水 cell phone...
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
水害被災者達は、防水の家具をそろえておけばよかったと口をそろえて言いました。
All the victims of the flood said they wished they'd had waterproof furniture.
完全防水するには、これを使うしかないよ。
If you want it to be 100% watertight, you have no choice but to use this.
この防水ブーツ、防水されているとはとても言えないな。この辺りを歩いてるだけで、足がビショビショになっちゃったよ。
These waterproof boots are far from being waterproof. My feet got soaking wet from just walking around here.