For thousands of years, sailors have used the colour of the sea to help them make sense of the waters they travelled through.
In many parts of the world this remains the most effective technique to this day and it offers a more reliable chart than even the latest electronics.
I took the above picture from an aircraft window recently and it gives some small insight into how this method works.
I discuss it in much more depth in How to Read Water.
Below is a picture of a yacht that has run aground amongst the sandbanks of Chichester Harbour. Look closely and you’ll see that the colours go light-dark-light-dark blue: shallow, deep, shallow, deep. It looks like this boat sailed a little too close to the light blue.
In the video above we are looking out, roughly west, from Brea Hill, see the chart below.
For more please see the book, How to Read Water:
Chart image credit: Navionics.