海域
hǎiyū · HSK 7
sea area
🌊 海 sea + 域 zone = sea-zone, a stretch of maritime space or waters
海 means sea and 域 means region or domain (as in 区域 zone, 领域 field). Together they name a defined area of sea — territorial waters, a fishing zone, a maritime space.
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).