What is the purpose of life jackets on a ship?

The purpose of life jackets on a ship is to provide buoyancy to individuals in water. This is crucial in emergency situations where someone may fall overboard or a vessel capsizes. Life jackets are designed to keep a person afloat, allowing them to conserve energy and maintain their head above water, which is critical for survival until rescue or assistance arrives.

Being buoyant, life jackets also help to keep the wearer's airways clear of water, vastly increasing the chances of survival in unforeseen maritime emergencies. The other options, while related to comfort or specific uses, do not accurately capture the primary life-saving function of a life jacket, which is to enhance the safety of individuals in water by providing immediate flotation support.