VHF radio - Satellite Phone
Marine VHF radio’s are used for standard communication between boats, but you normally need a VHF radio license to operate one.
Although waterproof radios are common, there are no VHF radio’s available to dive with. The only exception is the Nautilus Lifeline, thanks its special pressure and water-resistant housing. Handheld VHF radios are limited in operational distance and the dive boat or other boats nearby will need a VHF radio onboard in order to receive your call. The Nautilus lifeline also has an incorporated distress button that can send your coordinates to all boats (who have the technical equipment to receive the call) within a 50km range, but it needs an MMSI number, which in many countries is only given to ships. This limits the use of this specific device.
Another option is the use of a Satellite phone, but you will need an underwater housing for it. You can call practically anyone in the world with it and satellite technology makes it possible to determine the approximate position of the user.
The ENOS®-System is independent of, and does not require the aid of, other rescue systems. It comprises a receiver and one or more transmitters as needed by the operators and divers.
The receiver is the basis-station from where the rescue operation is initiated. After switching the receiver on, it indicates its position by GPS and is ready to receive and evaluate signals from the transmitter.
In case of need, the ENOS®-Transmitters have to be switched on by the diver, which are able now to indicate their own position, also by GPS. This position will be transmitted to the ENOS®-Receiver by a license-free radio-frequency. The position of the ENOS®-Transmitter, its distance and direction towards the receiver, are shown in an easy-understandable graphic on the display of the receiver.
Personal Location Beacon (PLB)
A PLB alerts search and rescue services by transmitting a coded message on the 406 MHz distress frequency to the nearest rescue co-ordination centre. If the PLB also has a built-in GPS it enables rescue services to accurately locate a diver to +/- 60 meters.
Once in the area, rescue services are then able to find the diver’s exact location using the inbuilt 121.5Mhz homing transmitter. Once activated the operation time is generally between 24-48 hours. PLBs are subscription-free devices, so have no cost of ownership after the initial purchase, but need to be registered to a person. Most PLBs though are not designed to dive with and only few manufacturers offer an underwater housing or have water/pressure resistant PLBs.
Other similar tracking devices are available but require an annual subscription to private companies or are limited to the 121.5Mhz frequency and/or GPS technology, making it less interesting compared to real PLBs.