It's by Tumblr user hollyoakhill, and she thinks that Ariel finds Hans in a shipwreck. I like to imagine it's more vindictive, and that Han gets pushed off the ship going home and Ariel somehow knows about his transgressions (maybe Anna has a shell phone for underwater communication) and decides to serve some justice. Mermaid style vigilantism, baby.
Okay, maybe my explanation has a few holes. The art is still awesome. What are your theories about the mash-up?