Teoatl

Teoatl is one of the three forms of "talismanic" magic native to the Maztica region of the Forgotten Realms. Its counterparts are Hishna and Pluma.

Unlike its counterparts, Teoatl is not part of the original Maztica setting, but was invented wholesale by the same madlad who took it upon himself to update the entire setting to Dungeons & Dragons 5th Edition by himself.

Teoatl, or Sea Magic, draws upon the magical energies inherent in flotsam and jetsam - shells, coral, driftwood, fishbones, etc - to manipulate water both directly and metaphorically - teoatl spells also include the likes of creating bioluminescence and enhancing the user's abilities to survive underwater.

In-universe, Teoatl is the newest of the Maztican magic styles, and was invented by the sister goddesses Nula, Watil, and Eha - though some claim it was actually invented by Azul, younger brother of Zaltec and Qotal, but he is allowing the sisters to pass it on to mortals to avoid getting into trouble. Its revelation has jumpstarted the faith of the three sisters, whose church is winning steadily more prestige, especially in coastal regions and riverside communities, where Teoatl is more obviously useful. The downside is that Umberlee is growing increasingly jealous of the three sisters for what she sees as challenging her dominion. Also, there are rumors that whoever "invented" Teoatl may have actually stolen it from the legendary palophonti, a race of giant aquatic scorpionfolk who inhabit the deepest trenches of the oceas off of Maztica's coast and who are likely to take a dim view of the theft...

Mechanically, teoatl is the same as the 5e adaptations of Pluma and Hishna; obvious subclasses for the Artisan and Wizard, and a Paladin subclass in the Oath of the Shark Knight; a seafaring Paladin who can turn into a shark.