Abstract: This invention is directed to a submerged combustion system comprising: (a) tank means for holding liquid, the tank means having a liquid inlet and a liquid outlet, and an exhaust gas outlet; (b) combustion chamber means positioned in at least a portion of the interior of the tank means; (c) means in the combustion chamber for enabling fuel and air to be introduced into the combustion chamber and being ignited to create a hot gaseous combustion product; (d) port means located in the combustion chamber means for enabling the hot gaseous combustion product to be exhausted from the interior of the combustion chamber into the tank means; (e) means for controlling the level of liquid in the tank means so that the hot gaseous combustion product passes through the liquid and the liquid heated by the hot gaseous combustion product is withdrawn from the tank means, and unheated liquid is introduced into the tank means through the liquid inlet; and (f) cooling liquid means located at the upper region of the combustion