I went out on the boat yesterday about 3 nautical miles out there was a wavy line and on the inland side it looked like a cleaner blue and on the other side it was dark blue?
In: Earth Science
There’s a lot more stuff in the water when you’re closer to shore. That stuff reflects a lot of light, but places without it absorb almost all the light. So you’ll get a different color near the coast than you would in the open water.
So when its a different color abruptly, its because there is a point where the shallow area abruptly stops, and there’s a current that keeps the stuff in the coastal water from going out any farther.
Is this near a river outflow? Assuming you’re not just seeing the coastal shelf drop off or something physical underneath the water, usually this happens where there are two radically different water bodies, like where a warmer freshwater river dumps into the ocean. The fresh water will rise above the salt water.
[For example, here’s where the Fraser river dumps into the Pacific just south of Vancouver CA in this video that explains it.](https://www.youtube.com/watch?v=qRClKxzJX9A) So what you’re seeing may not be quite as silty if its freshwater or you might be seeing the convergence of two different ocean masses of differing salinity.
Hard to say without knowing the specific location, but there’s a thing called a continental shelf that extends out a ways, generally a couple hundred miles at a depth of maybe 200 feet, from the shoreline of the continent, and then the ocean floor pitches down, often in an almost sheer cliff, to the so-called abyssal deep, which averages well over 10,000 feet. My guess is you were looking at that. And if that makes your balls crawl up, well join the club.
So was it a line parallel with the shore? Towards the island didn’t look as dark as away from the island? If so, it might have been a drop-off or a continental shelf of some kind. The continental crust ended in an underwater cliff, and there is now deeper ocean beneath you.
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