Updated: Aug 14, 2018
The War Turtle lives in the Land of Haze (the second floor of The Vapor Sea) where 85% of the vapor in floor has been polluted by man. This turtle, known by biologists and wildlife experts as the Red Snapper, hardened its shell overtime to protect itself from thick pollution. The turtle evolved to become red from eating a now extinct species of bird that went by the name of the "Flamingo." Flamingo's diets consisted of mainly brine shrimp which turned their feathers pink, so by eating the flamingo, the turtle turned pink and then red overtime as the bird became extinct and their color began to darken due to a change of diet.
They are now known as War Turtles since - while they have not been in war - the original intent was to breed them in captivity so that if war broke out that the Peacekeepers and Peaceholders would be able to traverse the sea quickly and avoid harsh weather conditions since animals can sense where poor weather will form. However, in the current day - the Platinum Age of Peace - War Turtles serve no purpose other than being locked in cages and being pitted up against their own species in "Dogfights." Dogfights are illegal - as stated in the commandments written by the Peacemakers - but the Peace Core doesn't act on stopping them since they tend to be busy dealing with Raiders, thieves, pirates, Grave robbers, etc.
They are also used for whaling (hence the harpoon).