海水浴
かいすいよく · kaisuiyoku · JLPT N2 · noun
sea bathing
🌊 海 (sea) + 水 (water) + 浴 (bath) = bathing in seawater, i.e. swimming in the sea
海水 means seawater and 浴 means bathing, so 海水浴 is bathing in the sea. The same 浴 appears in 入浴, bathing indoors in a tub.
海 — water radical 氵 + 每 (phonetic)
海 is a phono-semantic compound. The 氵 (water) radical signals the meaning—a vast body of water—while 每 supplies the sound. Originally referring to the sea or ocean, it later extended figuratively to mean 'vast' or 'a great quantity,' as in 人海 (a sea of people).
水 — pictograph of flowing water
水 is a pictograph depicting a stream of flowing water, with the central line representing the main current and the side strokes showing splashing droplets or ripples. In oracle bone script it was drawn even more clearly as a wavy vertical line with branches. It retains its original meaning of 'water' and also serves as a radical, often appearing in the compressed form 氵.