As a side note to some of you with newer marine VHF radios. The new DSC standard - Digital Selective Calling - allows boats with this type radio to contact each other without hailing over the open airwaves (where others listen in
) and without tying up another channel. I don't know the particulars but each radio has a code/handle that you can enter and find if it's in range.
Some models that interface with GPS can even send out locations to "allowed" DSC radios...
Just a thought