Why navies sometimes buy different small arms

Why do naval and army small arms differ in many countries?

Sometimes because of procurement rivalry or scale, and sometimes because an army weapon is not suitable for saltwater service.

Separate purchases can become an avoidable logistics failure when organizations insist on owning distinct equipment. A very large military such as that of the United States can sometimes absorb the cost because each service still buys in quantity. Material requirements can also justify a separate purchase: an army weapon may prove unsuitable around saltwater and force the navy to select another design. The answer distinguishes bureaucratic duplication from environmental requirements that genuinely justify a naval variant.