Back home, I did a couple of experiments. I mostly wanted to play with adding more color and framing, so in the first experiment, I first drew a frame to draw the picture in. I did no drawing, but started right in with the paint. (Thanks to Alisa Burke for giving me the confidence to try this!) Only after painting did I add a few details to the boat with pen.
I didn't like this much, the boat had "disappeared", so I tried another, cropping the photo so that the boat was more prominent.
I didn't like this as much as the original sketch either, which had more contrast between the elements, thereby emphasizing the boat, making it more dynamic:
These experiments were useful, although I realize now that I might need to do another one to fully decide about the framing.