Sentence:  Traveling at sea for the first time is a chance to realize that the ocean is not one ocean. The water changes. The Atlantic that seethes off the eastern U.S. is <WSD>glaucous</WSD> and lightless and looks mean. Around Jamaica, though, it's more like a milky aquamarine, and translucent. 
Meaning of the word marked with <WSD> tags:  Of a pale grey or bluish-green, especially when covered with a powdery residue.