What is the activation method for the 406 EPIRB (category II)?

The correct answer is that the 406 EPIRB (category II) is designed primarily for automatic activation when it is submerged in water. Category II EPIRBs are typically intended for use on vessels and are automatically activated when they leave the vessel, usually when water depth reaches a certain level, thereby sending a distress signal without requiring human intervention.

Manual activation is an additional feature that allows the user to activate the device intentionally, but it is not the primary method of activation for a category II EPIRB. While some other types of EPIRBs may allow for only manual activation or both methods, the main purpose of a category II EPIRB is to ensure that a distress signal is sent automatically in a situation where the vessel is identified as in distress.