Originally Posted by mattnone
...a last minute decision to go into a port/country that requires a vise and we were not aware of this what would be the first protocol for getting one and would there be any repercussion? ...
First off as master of the vessel it is your responsibility to know. In today's Internet
connected world there is really no good excuse for not knowing. All countries I've ever been to have official web sites such as consulate/embassy that list immigration requirements. Sites such as NoonSight have unofficial, but generally good info. And you can post here with specific questions.
Generally, as stated, the requirements are no different based on mode of transportation. If you require a pre-authorized visa for visiting a given country then you will be required to apply for one before arriving on a boat.
Bear in mind that a country does not have any obligation to allow you entry. They may just simply deny entry if your papers are not in order...then you are in a pickle: you can sail back to where you came from and correct your papers or attempt to sail into somewhere else which may also deny you entry.
There is no upside to showing up unprepared.