The Teenage Mutant Ninja Turtles are stoked when Professor McGuffin sends them on a special expedition to the ocean floor where the heroes are shell-shocked to discover TURTLANTIS, a subaqueous civilization that reveres turtles! But not all is as it seems under the sea...and when the fearsome fighters find themselves conscripted into a gladiatorial arena, they'll have to do battle against a familiar foe to get back to the surface...