All of these systems include the use of compact, wearable devices. Some look like wristwatches, key fobs and flashlights. Many are designed to attach to a life jacket or article of clothing. Some are manual, and others have automatic triggers that include water immersion, increased boat distance, and inflatable-life-jacket activation. Of course, their effectiveness hinges on skippers and crews wearing them religiously, day or night, in calm or rough seas.