As we're planning a trip to the tropics, we thought window shades would be a good idea. So I bought some vinyl black (not blue as it appears in the photo) mesh fabric from Sailrite called Phifertex, which has a number of outdoor uses and provides 70% sunshade but still gives a good view.
I wanted to make them in 2 pieces only, one for each side of the boat, to make them easy to take off and on. So I made a paper pattern and sewed 3 pieces together so it could accommodate the curve of the windows towards the front of the boat. Plus the window sizing wasn't uniform which didn't help.
I ran some black vinyl tape around the edges for strength and finished the edges with black marine grade bias binding. Black snaps were added which will be attached to adhesive sockets on the boat (which means no drilling - hooray).