Rainbow Snowcone AU: A Little Different Up Close

Honestly, this could also be titled "I am going to paint with all the colors of the wind and NO ONE CAN STOP ME"
(But also, look yonder! Is that an actual, legitimate background behind Jack and Tooth?!?! By Man in the Moon I think it is~)
Anyway, this is my contribution to the Rainbow Snowcone Week "AU" prompt. So, here's my Mermaid!AU for Jack and Tooth...

In this AU, Jackson was found wandering around the seaside port town of Burgess by Mrs. Bennett, owner and main headmistress of the local orphanage. After realizing the boy had a severe case of amnesia, she took him under her wing, cared for him along with her other charges, and even gave him the temporary surname of "Overland" since the boy could not remember his own. That same year, Jackson (who prefers to be called "Jack" and is adventurous as the day is long) came across a rather unusual new friend while wandering around the tide pools of Burgess's shoreline. At first glance, Jack thought he saw a dark-haired girl around his age caught in the currents and large pieces of driftwood in the shallow waters. Upon helping her escape the debris entrapping her, Jack found himself face-to-face with a mermaid with violet-pink eyes and green scales. Though she was initially skittish, the little mermaid introduced herself as Toothiana ("Tooth" for short) and thanked Jack for his help. From that day on, the two found as many opportunities as they could to meet and explore the coves, caves, and beaches around Burgess. Both have their own stories to tell, and both are fascinated with details about life above and below the waves.

Ten years later the two are still thick as thieves (though certain crushes may have developed over time, to the general personal denial on both sides). While Tooth diligently performs her duties as princess of the underwater kingdom known as Punjam Hy Loo (and as a big sister to her ten little sisters, the youngest of whom is known affectionately as "Baby Tooth"), she still makes time to see her oldest, dearest friend. Jack, in turn, balances helping out at the orphanage (where he is a big brother to all those living under Mrs. Bennett's roof, especially the headmistress's own children: Jaime and Sophie) with his day job as an apprentice to the greatest craftsman/artisan the town has ever seen: the fierce yet wise and kindly Nicholas St. North. Still, he takes every chance he can get to steal away to see his partner in crime/adventure. All goes well until one day Tooth's kingdom is attacked by mysterious, evil water-horses comprised of shimmering black sand. Tooth alone is able to escape (as she was up on the surface during the attack), and now it is up to her and Jack to rescue the residents and powerfully magical artifacts of Punjam Hy Loo as well as discover the secrets connected to the distant mer-kingdom known simply as "Frost" and Jack's missing memories...

(I'll give you hint as to who the bad guy is...It's Pitch)

Anyway, characters belong to Dreamworks, but this AU and fanart belong to *GossamerWing