Here is another approach you might want to see.
First I have sketched a few impressions of the lighthouse on Patos, in the San Juans.
From there is did 4 watercolour painting sketches to see what I might like as a layout for a future painting. The watercolour paintings are about 7 1/2" square on 200 lb(I think) cold pressed watercolour paper. I used acrylic paint to get the richer colours.
If you are interested in any of them they would be $25 each.
Lighthouse 1 $25