What type of life jacket is known as a throwable device and is not meant to be worn?

The correct answer is Type IV. This type of life jacket is specifically designed as a throwable device, meaning it can be thrown to someone in distress in the water rather than being worn at all times. Type IV life jackets are not intended for continuous wear; instead, they are often a device such as a ring buoy or a cushion that can be easily thrown to assist an individual who has fallen overboard or is struggling in the water.

In contrast, other types of life jackets such as Type I or II are designed to be worn and provide buoyancy to keep the wearer afloat. Type V life jackets also require being worn, and they come with specific conditions for use whereas Type IV does not. Understanding the purpose and use of each type of life jacket is crucial for ensuring safety on the water.