Besides the necessity to maintain watertightness (generally known as watertight integrity), there is a need to keep out of the ship radioactive material, and biological and chemical agents (all included under the general name 'gas ').
Ngaphandle kwemfuneko yekugcina ukungangeni kwamanzi (ekwaziwa jikelele njenge-mfezeko yekunganeni manzi) kukho imfuneke yokuge ina ngaphandle kwenqanawe imitha ebangwa kukuqhekeka kwe atom, ne biological mechanical agent eziqukeneyo kwigama, eliqukayo elingu gasi.