What is the primary purpose of wearing a life jacket while boating?

Wearing a life jacket while boating is primarily intended to provide flotation and safety in the event of falling overboard. Life jackets are designed to keep a person's head above water and to help maintain an upright position in the water, significantly increasing the chances of survival if someone finds themselves in an emergency situation, such as an accidental fall into the water. This safety device is crucial because it allows individuals who may be unable to swim or who may be injured to stay afloat until help arrives.

The other options don't contribute to the primary life-saving function of a life jacket. For instance, while staying warm in cold weather is important for overall comfort and safety, the primary function of a life jacket is not temperature regulation. Similarly, looking fashionable or preventing sunburn are not relevant to the safety features that life jackets provide. Thus, the correct answer reflects the essential role of life jackets in promoting safety on the water.