The Dornier Do 18 was a development of the Do 16 flying boat.
The Do 18D 79 built, was the first military version, powered by two 450 kW (600 hp) Jumo 205C engines, armed with one 7.92 mm (0.312 in) MG 15 machine gun in the bow and dorsal positions.
The Do 18G 62 built, was an improved version, powered by two 656 kW (880 hp) Jumo 205D engines, armed with a 13 mm (0.51 in) MG 131 machine gun in the bow, and a 20 mm MG 151 cannon in a power-operated dorsal turret.
This version had an altered bow contour and broader sponsons
The Do 18H was an unarmed dual-control training version.
The Do 18N was a designation for unarmed air-sea search and rescue conversions.