滄海[soukai] blue waters
滄海一滴[soukaiitteki] a drop in the ocean (bucket)
滄海桑田[soukaisouden] The word is a scene of constant changes (as the blue sea changing into a mulberry field). (Chinese legend)

桑田滄海[soudensoukai] The word is a scene of constant changes (as a mulberry field changing into a blue sea). (Chinese legend)
滄溟[soumei] great blue sea
滄浪[sourou] blue waves