I am going to amend my post slightly to provide clarification.
You are NOT required to have a license if you are operating a portable VHF radio under part 80 on a VOLUNTARY vessel (i.e. one not required to have one)
You may use that radio for all applicable uses of a marine radio, including ship to ship, ship to shore, etc.
You are NOT required to have a license for operation of a portable VHF radio from shore UNLESS you are providing a service (public coast station, private coast station, utility station) for commercial or non commercial use. There are some examples in the link provided by nd5y above. In fact, i'll quote it here:
The basic example I can think of for using a portable on shore outside of the above would be communicating ship related information with a member of your own group or party.
HOWEVER. This is what I mean by "appropriate under the rules" Marine radios are for marine transmissions. As such, routine communications between members of your group or party on a ship and on shore probably are not appropriate. You cant just leave a portable with someone back on shore so they can tell you when the burgers are hot and the beer is cold.