領海
りょうかい · ryoukai · JLPT N1 · noun
territorial waters
🌊 領 (territory) + 海 (sea): the sea that counts as your land, ryoukai.
Sounds like 'ryo-kai', close to 'ryo' (territory) and 'kai' (sea). Think of the sea a country claims as its own, out to the coastal limit.
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).