I have a Standard Horizon HX850S handheld DSC VHF radio and the manual indicates that no license is required in the US. It is hard to believe it is not subject to the same rules as the Nautilus Lifeline.
I downloaded the manual from Welcome to StandardHorizon.com
The relevant paragraphs from Page 8 (bolding is mine):
MARITIME STATION LICENSE
An FCC ship station license is no longer required for any vessel traveling in
U.S. waters which uses a VHF marine radio, RADAR or EPIRB, and which is
not required to carry radio equipment. However, any vessel required to carry a
marine radio on an international voyage, carrying a HF single side band radio-
telephone or marine satellite terminal. FCC license forms, including applica-
tions for ship (605) and land station licenses can be downloaded via the Internet
at FCC Form 605. To obtain a form from the FCC, call
(888) 225-5322.
MARINE RADIO CALL SIGN
Currently the FCC does not require recreational boaters to have a Ship Radio
Station License. The USCG recommends the boats registration number and
the state to be used.
The question of a license has not been at issue in this thread. The fact that the FCC doesn't require a license for Marine VHF use on small boats has been previously stated and understood. What's being discussed here is whether use of Marine VHF radios by a diver not associated with a boat is legal, licensed or not, or alternatively, whether the FCC would consider a diver to be a "vessel".
I'm not attempting here to add anything to that discussion, I just wanted to point out that the post I'm replying to hasn't, either.