Having been originally developed from the Supermarine S6B it is perhaps natural that the Spitfire should be developed for use on water.

The first Spitfire floatplane was a conversion of a Mark I, the so called "Narvik Nightmare" R6722 which was produced at the time of the German invasion of Norway where there emerged a requirement for a fighter capable of flying from the Fjords in view of the lack of suitable airfields in the country.
In the interests of speed, floats from a Blackburn Roc were fitted but the trials were not successful and as the campaign for which the conversion was required was rapidly drawing to a close the project was suspended.

The idea was revived again with the beginning of the war in the Pacific against Japan when it was realised that a floatplane fighter with good performance would be an essential asset in the island campaigns which seemed likely.
Folland Aircraft undertook the conversion of a Spitfire Mk Vb, W3760, with Supermarine designed floats and this aircraft proved an immediate success with a top speed of 324 mph. In this aircraft the carburettor air intake was extended to avoid spray, a shorter four blade propeller was fitted, cantilever pylons attached the floats to the inboard wing sections, a ventral fin replaced the tailwheel and the fin was extended slightly forward to increase the vertical tail surface area.

Folland built several sets of floats and converted another two Mark V aircraft, EP751 and EP754. These together with W3760 were shipped to Egypt in 1943 and assembled with the intention of covertly operating them out of small Greek islands to intercept German transport aircraft.

A further Spitfire was converted in 1944, a Mark IX serial MJ892 powered by a Merlin 45. The performance of this aircraft was superb and with a top speed of 377 mph the fastest floatplane of the entire war.

Dave and I originally put the floatplane together for ourselves