How many flotation devices must a legal working boat possess?

The legal requirement for a working boat is to have at least one flotation device on board for every person on the vessel. This ensures that in the event of an emergency, there are enough flotation devices available for each person to potentially aid in flotation and survival.

While having more than one flotation device can enhance safety, the minimum legal requirement establishes a baseline to ensure that everyone aboard has access to one. This is why the correct answer indicates that a legal working boat must possess at least one flotation device.