Dedicated Water Thruster - The Propeller

Electric fan motors for atmosphere and for aqueous environments differ in principle only in the speed of rotation.

Basically, it is only a question of how much air or water (in kilograms) and at what output speed the motor can pump from the inlet side to the outlet side.

Chris - The compressibility of air and the "incompressibility" of water are irrelevant - air is "light", so you need to achieve a high discharge velocity to achieve usable momentum. Therefore you need to both compress it and heat it. Water is "a thousand times" denser than air - so you don't need to either compress it or heat it - and you don't need such a high discharge velocity either. You can achieve the necessary Momentum at the outlet with a simple vane pump.

I tried this in another game - Kerbal KSP - and it works great, just swap the medium air for water and a bit of fiddling with the numbers.

Lets have a few types with different profiles for different purposes.

I personally like this one a bit.

My ZIL-4906 "Sinaya Ptica" for KSP. Two "waterjets" are behind the rear wheels. The used model is the jet engine from the game.

Max. speed on water with 2x waterjet ~50km/h (13,7m/s), with whell only~12km/h (3,4m/s)

Nice duck