礁石
jiāo shí · HSK 7
reef
🪨🌊 礁 jiāo = rock radical 石 + 焦 jiāo (scorched/sound clue); 石 shí = stone. Reef = sea-rock.
礁石 literally pairs 礁 (submerged sea rock) with 石 (stone). The 石 radical on the left of 礁 flags stone; the right side 焦 jiāo just lends the sound. Two stone-words stacked: a reef is a stone hazard hidden at sea level.