Quick Answer
Personal Locator Beacons (PLBs) do not work underwater, as they rely on a line of sight to the satellite system and cannot transmit signals through water.
How PLBs Work
Personal Locator Beacons (PLBs) use a satellite-based system to send distress signals to emergency responders. When activated, a PLB sends a 406 MHz distress signal to the Search and Rescue Satellite-Aided Tracking System (SARSAT). SARSAT then relays the signal to local emergency responders, who can locate the beacon’s owner. This process typically takes around 5-10 minutes.
Underwater Limitations
PLBs are designed to be used in emergency situations where the user is on or near the surface of the water. When submerged underwater, the signal cannot be transmitted through the water due to its high frequency and the properties of water. This makes it impossible for PLBs to send distress signals underwater. In fact, the signal from a PLB can be disrupted by as little as 1-2 inches of water, making them unreliable in underwater situations.
Alternatives for Underwater Emergencies
For underwater emergencies, other devices such as Emergency Position-Indicating Radio Beacons (EPIRBs) or Personal Markers (PMRs) may be more suitable. EPIRBs are designed to be used on vessels and can send distress signals from underwater, but they require a more complex setup and are typically used on boats rather than personal use. PMRs are small markers that can be attached to the user and can provide a visual signal to rescue teams, but they do not send distress signals.
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