A truck bed having a flat bed deck adapted for mounting on a truck to haul cargo and a tank within the deck adapted for containing and hauling liquid. The deck includes a top plate, bottom plate, front end, rear end and sides. The sides are connected between outer edges of the front end and rear end. The top plate is connected to the front end, rear end and sides. The bottom plate is connected to the front end, rear end and sides. A tank is formed by the top plate, bottom plate, front end, rear end and sides, whereby the sides are connected in a seal state for holding the liquid.