What causes colors in the ocean?

I just sailed back from Bermuda. In Bermuda the water is an incredibe blue color, which changes a bit based on bottom structure (sand or coral), and sunlight or cloudy, and depth of water. As we sailed back the ocean depth increased and the color went from this beautiful deep blue to an almost purple color. We went... show more I just sailed back from Bermuda. In Bermuda the water is an incredibe blue color, which changes a bit based on bottom structure (sand or coral), and sunlight or cloudy, and depth of water. As we sailed back the ocean depth increased and the color went from this beautiful deep blue to an almost purple color. We went through the gulf stream, and I was too intent on the helm to notice the color of the water, but then after the gulf stream the water turned a dark blue to a greenish blue.

The crew had long arguments about this that were thankfully broken up by the sighting of a shark.

I thought that silt runoff from rivers allowed greater plant diversity, and therefore more yellow tint (blue plus yellow =green)

R thought that the color was a result of pollution.

C brought in that the gulf stream acts as a barrier, and water on the inland side is of different temperatures, and supports plant and microbrial life.

J&B had ideas but were too smart to get involved.

any clues?
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