This is wonderful, and I'm not surprised considering how well that wedding venue map of yours turned out.
The colors really bring things to life without at all feeling cartoony or out of place. One need look no further than Francesca Baerald to know how lovely a watercolor style can look on a thematic map, and you've done a great job executing it.
Zooming in some of the lineart feels a bit fuzzier than I might like on certain features such as the sea serpent, but since it's just a test for now I don't know if that's just a side-effect of doing that quickly. It's hardly noticeable, anyhow. Awesome job overall, and I'm looking forward to seeing more from you!