There is a marina near Cairns, Australia
. Built by a real estate developer and called Bluewater
Marina. To date no one has seen it as being blue. Brown, green, iridescent from oil
But this probably confirms the common view about real estate developers fudging the truth, rather than the reality of the ocean's colours.
In many tropical areas, the coastal regions are usually muddy due to the heavy rainfall. Around most coastal cities any rain produces muddy water due to excessive land clearing. Darker, thus warmer water probably contributes to global warming as well. Stir, stir.
The observation that the colour we see is what is left over - reflected - from the incident light after absorption, may account for the twinkly effect sometimes observed after a few beers and watching the sea at night. Or it could be stars or the moon or noctiluca scintillanis
Also, according to my wife, whenever I talk about the mood of the sea, she jests that maybe the colour is actually a display of the ocean mood. Very philosophical. Blue for sad, green for jealous, brown for shitty. If pink or yellow, then you are probably drunk or the sunset has got at you.