Recently, a family member went on a cruise, it was shorter than 28 days, and it was not a problem to use the vapor pens on board but they do typically have a smoking area that it will be designated. It is a far different matter with the airlines, don’t carry cannabis on the airline because that is against federal law.
You must also keep in mind that if the cruise is leaving from a state that does not recognize cannabis as a legal substance you could be taking additional risks.
There is some concern for maritime laws also since a cruise could take place in maritime waters.
Bon voyage
drolson