Hmm...well, let's see here...
Mermaid dies, when she finds out the Prince she loves actually loves the Witch.
Witch & Prince get married.
The Prince now has a Trident that can control the ocean.
And the Witch is clad in a black wedding dress, and the Prince and her are...going to rule the world?
This was based on another idea I had that I used for my AP Drawing Portfolio. In that version, the mermaid actually pushed the Prince off board and choked him to his drowning death while she faded away. So it was yandere!Mermaid.
This version, the "wedding" is on the beach.
Hey look, gradient overlays and masking layers. P:
I don't know how long my drawings take...I scatter the time and watch anime/vocaloid/MADs while I work...
Can you see the mermaid breaking away?