VERY nice composition, the visual flow is quite entertaining!
My only critique, is that the moonlight needs to be more consistently bright overall. The distance of the Earth to the moon means that the illumination is pretty much equal, like sunlight - not brighter on the horizon, fading to darker towards the viewer...This means the mermaid, the rocks, the ship, and all of the water need to pretty much be the same value.

Otherwise, this is really good work!

too dark

Nice work author...gl

You should intensify the lights.

Nice but it may be little to dark

ok i lighted up the image a bit and add a new layer en filled it with a light blue color set it to linear light and lowered the opacity to make the colors more equal, hope its ok now and thx for for the comments