Jane-Doh,
Sea planes always fascinated me as a child. The Seamaster was intended to deliver nuclear store. Polaris systems were used instead.
You are correct; the Seamaster did indeed have afterburners. They were intended to provide additional power on take off. Unfortunately a slight fault in the design was found; the engine nacelle design was such that when in afterburner mode had a tendency to burn the rear fuselage and induce sonic fatigue.
The two afterburning jet engines were located side by side in each of' two nacelles mounted on top of the wing immediately adjacent to either side of' the fuselage. (The afterburners, an unusual feature for a large subsonic aircraft, were for use oil takeoff.) Inlets swept back at nearly the same angle as the wing leading edge were found to be unsatisfactory and unswept inlets were finally adopted; exhaust nozzles were behind the trailing edge of the wing.The location of' the engines was, of course, strongly influenced by the necessity of minimizing spray ingestion during operation on the water.
I copied that last paragraph from P6M SeaMaster. Go have a read