Floats or a boat hull did not automatically disqualify a First World War aircraft from air combat. Purpose-built fighters were still relatively slow, and aerodynamic streamlining had not reached Second World War standards. Some flying boats and seaplanes could compete as fighters within the limits of their era. The Hansa-Brandenburg W.12 and Macchi M.5 make more sense in that technological setting.
Notable Point · 8:28-8:49
Why a flying boat could still be a credible fighter
Low fighter speeds and immature streamlining allowed some waterborne aircraft to compete in aerial combat during the First World War.