It is proposed that the seal arrangement for flood protection within domestic and commercial door units is an active system which, when submerged, uses the pressure of the flood water to create a watertight seal, thus preventing ingress. Utilising a Stratasys J750 PolyJet 3D printer, prototype seal designs were rapidly developed, trial fitted into sections of door frame profiles, and finally tested in-situ in flood tanks to ascertain the success of the design. Sections of seal, fitted to a flood depth of 450mm were tested under pressures of up to 3.5 kPa, with no ingress detected until 300mm depth of water. Further testing is ongoing to test the seals to higher water levels and over a longer duration of time, before committing to commercial manufacture of the final design through a higher volume extrusion process.