Thanks Alan - very instructive. I never had much luck with the radios we were issued with for diving. In fact I did suggest we could improve the range by tying a chinagraph pencil to the aerial and sticking some white fablon to the back of the radio. That way we could write a message on the plastic and throw the radio to the recipient!
Just as a follow-up.
The VHF I carry with me is capable (and programmed) for :
All marine frequencies
All Coastguard frequencies
All UK SAR (Land & Sea) frequencies
Amateur (Ham) 2 metre (144Mhz) channels
All PMR446 ('walkie-talkie') UHF Frequencies
Edit to add :
Forgot to mention that this radio transceiver also include a 'standard' VHF receiver (music, news, etc channels), an LED torch and a very bright 'strobe light' to assist rescuers in finding you.
I have used 'radio' for many, many years and DX'd all over the world but I'm really impressed with the features that this little radio offers for a 'pocket-money' price.
Cost of the Radio Transceiver was £13* + £3 for a programming cable. Comes with a 1800Mah battery as standard but I have changed that out to a 2700Mah at a cost of £9. Added at 'better' (longer) aerial that gives (allegedly) a 3.0Db gain - cost £1.40
Battery charged via USB cable from my 'power-pack'.
Weight of radio including 'extended' battery = 240 grams (8 oz)
* There was a 'price war' going on so I bought several whilst they were on 'offer'. They are normally about £18-£20
I am a 'lapsed' Ham (G3LCR), and have both a marine VHF operators licence and an Aircraft VHF operators licence.
However I should point out that the radio is 'illegal' for transmitting (except in an emergency) as it works on multiple frequencies so is not 'type-approved'.