What is a "lifejacket" used for?

A lifejacket is designed primarily for safety, particularly in situations involving water activities such as boating, swimming, or any situation where there is a risk of drowning. Its main purpose is to keep a person afloat in the water, thus preventing accidents and saving lives. When worn correctly, a lifejacket provides buoyancy and helps to ensure that the wearer's head stays above water, reducing the chances of panic and enabling them to stay safe until help arrives or they can reach safety themselves.

While staying warm in cold weather or assisting in swimming might seem relevant in some contexts, those are not the primary functions of a lifejacket. Additionally, using a lifejacket to display style at the beach overlooks its important safety function, which is critical when participating in aquatic activities. Thus, the correct choice highlights the essential role lifejackets play in boating safety.