Actually, any WHTI-complaint document is valid when using both land and sea crossings to enter participating countries in the Western Hemisphere. The most common example would be cruises around the Caribbean, where many countries now will accept the US Passport Card (a WHTI-complaint document) instead of a passport book. At the end of the cruise, you could use the Passport Card to re-enter the USA, as long as your cruise did not call at any ports outside of the USA/Canada/Mexico/Caribbean/Bermuda.

More details at:
http://www.getyouhome.gov

In order to use designated NEXUS reporting stations when entering Canada via private vessel, the WHTI-compliant document must be a NEXUS card. Same goes for entering Canada by land using designated NEXUS lanes. In both cases, this restriction is because NEXUS membership involves vetting by CBSA in addition to US CBP.


Based on the way the marketing and discourse are evolving on the NEXUS and GlobalEntry websites, I suspect that CBP and CBSA are in the process of integrating all of these programs (NEXUS, SENTRI, GE, and perhaps even FAST) into a single Trusted Traveler program, valid for land, air, and sea entry to participating countries. Other countries (such as the Netherlands) are getting involved as well.

It would be fantastic if a majority of developed countries in Europe and the Americas could join together and offer reciprocal privileges for trusted travelers who have passed extensive background investigations and meet the "low-risk" criteria. It certainly would make life a lot easier for those of us who travel extensively and dislike waiting in lines and using up the time of passport control agents who really should be focusing on others.