Brownsea Island is a favourite place of mine; I just wish I could get there more often. It is lovely to be remote from the daily hustle and bustle, in a place where where you are is more important than what you are.
I was sat on the ferry waiting to cross to the island yesterday and it occurred to me for the first time, Brownsea Island, the island in the brown sea, and sure enough, despite the blue sky the water did look brown rather than blue! I had never thought of that before.
It does not take long to figure out why this is of course. Poole harbour is very shallow and even at high tide the water is not very deep and so the dark brown mud influences the colour you see, after all, water is colourless. Also at high tide large areas of eel grass and spartina grass become submerged in water making for a brown effect on the water swamping it.
So yes, Brownsea Island is an island set in a brown sea, it is aptly named.