This list contains all amphibious cars including prototypes I know about. For definition - I am talking about cars, no trucks, no ATVs, no amphibious working machines or that kind of stuff. Those vehicle listed are road- and seaworthy (or were designed to be) and designed for passenger carrying.
All vehicles listed are in chronical order.
Because of being split into many pieces and it took too much time to load all pictures at once, I have split the century into ...

1899	no picture	Magrelen Amphibium	Danmark, combustion engine
1904	no picture	unknown	Germany, boat on operating wheels
1905		Richmond	USA, three wheeler, paddles on backwheels
1906		Fournier	France, not sure if really built
1907		Ravaillier, Canot-Voiture-Touriste	France
1909		Amphi II	USA, made by Admiral Howell and his son
1913		Lambert Cyclecar	Scottland
1913		Garbaccio	Switzerland, air-propeller
1914	no picture	unknown	Belgium, unsuccessful crossing of the English Channel
1914 -1917		Hydromotor (Delia)	USA, small production, maybe a handful cars
1915		Johnson	USA, 4-seater built, 2nd car 2-seater racer not proofed if actually built
1915		Zeiner, Hydro-Automobil	Austria, Prop removable
1917		Monnot, Hydrocar	USA, wheels + axles removable, runs backwards in water
1920	no picture	Metcalf, Amphiglyder	England, air propeller
1921		Autogen	Germany, three wheeler
1922		Vargoz, Auto-Amphibie	France
1922-1924		Mathieson, Seacar	England, rescue boats on Ford T chassis
1923	no picture	Barnes, Amphibian	England, bigger Mathieson version
1923	no picture	Robinsons, Silver Spray	England, another Mathieson copy