File:Propeller-cased ship without hydrofoils.PNG

A schematic showing how a casing for the propeller needs to be added with non-hydrofoil ships. A casing allows several advantages: it eliminates the risk of fatal accidents (with crew, dvivers, ...), it eliminates damage to marine species, it reduces the risk of damage to the propeller (eg from floating objects as ropes, materials, ...), it may finally also increase output power similar to the working of a pump-jet. The casing can be added do-it-yourself, as too the hydrofoils, also (though not required), the engine can be converted to run on (oxy)hydrogen or liquid nitrogen. Note that the water supply pipes need to have an cumulative equally large diameter as the propeller casing; thus when using 2 water supply pipes the diameter of a single pipe needs to be half that of the casing.