What a crew needs to remain at sea for weeks

What does designing a ship to spend a long time at sea mean, and which parameters matter?

It means providing accommodation and support for weeks or longer, including proper sleeping places, toilets and washing facilities, food storage, and provision for crew health.

A ship intended for extended sea service must support its crew beyond an overnight passage. Bunks or hammocks provide sleeping places suitable for repeated use. Toilets, showers, and food storage have to support the number of people aboard over a prolonged period. Modern ships may also include gym facilities because maintaining crew health is part of endurance.