The Ruffwear Swamp Cooler uses natural evaporative cooling to keep dogs cool. Clients soak the vest in cold water, wring it out and fasten it around the dog. Evaporative cooling exchanges the dog's heat as water evaporates from the coat's reservoir. The vest’s wicking outer layer facilitates evaporation, the absorbent middle layer stores water for evaporation and the inner layer transfers the cooling effect to the dog. Temperatures drop through the phase transition of liquid water to water vapor, mimicking the cooling effect of humans' sweat. The vest's light color is designed to reflect heat from the sun. Auto-lock buckles on each side of the machine-washable jacket provide easy on and off.