What does 海水 mean?
海水 is a Japanese noun meaning “seawater, saltwater” in English. It is written as 海水 in kanji, かいすい in hiragana, and kaisui in romaji. This word is part of JLPT N3 vocabulary.
Example sentence
海水が傷にしみて痛いよ。
The seawater stings my cut.