The Macchi M.C. 72 was an experimental seaplane designed and built by the Italian aircraft company Macchi Aeronautica.

It set a new world speed record (over water) on 10 April 1933, with a speed of 682 km/h (423.5 mph). It was piloted by Warrant Officer Francesco Agello (the last qualified test pilot). Not satisfied, development continued as the aircraft's designers thought they could break 700 km/h (434.7 mph) with the M.C. 72. This feat was in fact achieved on 23 October 1934, when Agello piloted the M.C. 72 for an average speed of 709.2 km/h (440.7 mph) over three passes. This record remains (as of 2016) the fastest speed ever attained by a pistonengine seaplane.

https://en.wikipedia.org/wiki/Macchi_...

footages from Aeronautica Militare