Thus spake "Douglas W. \"Popeye\" Frederick"
<Popeye@finalprotectivefire.com> :

Yeah, but don't the track you?  I know Roadway does, friend of mine
worked on the project for them.

I think it mostly depends on the kind of contract you have.

For instance, in Sibiria, we all had similar cell phones.
Only the Swiss guy with a time based regular contract could
do calls there, Christiane couldn't do anything except have
an idea that she the could ( reality mismatch), I was at
least recieving system voices telling me why it didn't work,
but was able to send SMS, while in Moscow, with booked in
with a different local company, they even could tell me in
an intellegible language, that making calls chances were
cancelled.
Screw prepaid.

Matthias

The point was that some VHF ham bands and ham licensing in general is
not world wide. You have to get permission of the local government to
use a US ham license outside US territory. The same applies to marine
band radios. The FCC licenses the radio, not the operator, in marine
and commercial bands. In Amateur radio, the operator is licensed under
FCC Part 97 so both diver and boat pilot would need licenses unless
you can call the system "automatic control". In that case the boat
pilot could not manually initiate a query event and cause the system
to transmit. (Being legalistic here.) You (generally) don't have to
obtain special permission to use a cell phone where coverage is
available so licensing and portability is not a concern.

Marine band direct links are probably preferable but are modular and
more of a kit since you would be putting together a marine handheld
and a GPS and doing it all with some kind of TNC to handle the digital
info.

Using an EPIRB or ELT is out of the question since the OP's intent was
for routine use to maintain a more or less constant watch on distance
and bearing to target.

The primary concern with a cell phone implementation will be line of
sight coverage for the phone on the surface of the water and the
ability to use the digital features of the phone when accessing the
cell network.

In the US and territorial waters a quad band phone is probably
overkill and a Blackberry is very suitable. Internationally, if a
"quad band" phone is a necessity, then you might have to resort to
something like an iPhone to obtain a comparable level of GPS, GSM, and
multimedia experience while you await your boat pickup or helicopter
rescue. The advantage of the iPhone over the Blackberry is that you
can take 2 megapixel video or stills of the circling sharks or record
your last will and testament in high-quality MP4 stereophonic sound.
Don't forget to put the phone back in it's waterproof container before
you die.