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.