Below is a watercolor I did a few months ago.While I was painting it, I thought it would be interesting to take in-progress shots for fun. So I will put the photos from start to finish (without the first pencil sketch.)
Inked drawing on watercolor paper
First couple of washes. Light background, darker tones, green on seaweed.
More color. Seaweed.
I added details on the figure and darkened areas.
I felt that the extra seaweed was too much so I added more ultramarine to cover them and add more depth to the water.
For this finished piece, I added details like the fish shadows in the distance and used white gouche to pick out details on her scales and fins.