Yey, you posted it!!! I really like the realistic look of the characters in this piece and the great perspective used here. The colors are very warm, happy, and islandy, very harmonious as denoted by the Bay of Harmony lol.
As for critique, although we already discussed this piece in class, of course, as already mentioned the values could be punched up even more. I used to have a big problem with this; I was terrified of using extreme values even in digital art. Even though you wanted to experiment in using pure watercolor, you can still take leaps with experimentation. After all, Ed Briant respects the exploration more if it's more risky. And since most of us were taking risks with using a new medium, we have to take it a step further to stand out.
To make the painting more interesting, character design is also another element. Right now, the merfolk look like normal human beings above the surface of the water. You could adorn them with more; jewelry from their culture, an unusual skin color adapted from their environment, gills, spots, you can go crazy with it! Same with the island folk, they could also have more unique jewelery or crazy hairstyles.
You have a good handle on watercolor from what I can see, so don't be scared to experiment with other media. Also from class, you can use crazy lightsources to promote more interest.
I hope you find this helpful, and I'll see you on Monday!!
Yes, all of those things would have been more within my grasp if we had been able to start it right away and work on it for two weeks. Painting it in one night is not recommended. But it was a lesson well-learned. Thanks for the input!