Canadair CL-215 air tanker. Canadair also made a turbine version, called the CL 415.
Since the demise of most of the heavy air tanker fleet in the US, the Canadairs have become one of the major fire fighting assets. THey are all fairly old airplanes, though. I don't think any have been built for over 20 years.
There are far more of these in Europe than in North America.
Two man crew, they land and scoop 1400 gallons at a scoop of water, and are capable of injecting fire fighting foam into the water as they scoop. The foam acts as a wetting agent.
The Martin Mars, of which there are two, have been privately operated by timber companies in BC for years. THey have recently been operating in southern CA on the fires around San Diego. Unlike the CL 215, the Mars are true flying boats--no wheels. The Mars are for sale, last I heard--HUGE airplane.
MTV