Some TMNT stuff really isn't for little kids.
Shelton Slujj was a billionaire land developer and philanthropist in the Pacific Northwest. Slujj bought a patch of forest for the purpose of safely disposing hazardous waste. The Ninja Turtles, April, and Splinter were technically camping on his land, but instead of having them arrested for trespassing, he asks them to patrol his facility to catch a saboteur. Raphael encounters the suspect, who turns out to be missing eco-terrorist Victor Fosse. Fosse says that Slujj's method for compressing the waste has been making it more dangerous, and that his Slujj-bots are handling the materials clumsily. Even worse, the temporary storage site for the waste until the facility can be erected is a ravine where the Sasquatch are living.
Slujj orders the Slujj-bots to apprehend Fosse, and a fight between the robots, the Turtles, and the Sasquatches breaks out. Slujj's daughter Emmy wanders off and falls into the ravine.
The fight defuses and April convinces Fosse and Slujj to hash out their differences with a discussion. Slujj takes them all to the ravine to prove that his storage methods are safe, only to find a poisoned and unconscious Emmy. Fosse sends for a Sasquatch shaman, who brings some herbs to cure Emmy, and Slujj vows a safer way to dispose of the waste, and to never clear cut forest land again.. This is a promise that he has kept ever since.
Later, as a thank you to their role in saving his daughter and redirecting his business to be more environmentally friendly, Shelton takes the Turtles out on his yacht for a vacation to Hawai'i. On the way there, their yacht is attacked by a sea serpent by the name of Umihaha. They are rescued by Kai Nezumi, but then locked away by the captain of their ship, Yuuki Agamatta, who is on the hunt for the serpent to get revenge for killing his nephew and badly wounding him. Kai lets the Turtles and the Slujjes free, saying that this vengeance kick his captain is on is an all-consuming self-guilt trip he feels for getting his nephew killed. The Turtles try to stop Agamatta, but Umihaha returns and destroys his ship. They are saved by one of Umihaha's children and the Turtles telepathically convince Umihaha that they are of no harm. Umihaha takes the Turtles, the Slujjes, Kai, and the unconscious Agamatta to the remains of his ship and offers to tow them to land.