Emails from a U.S. boater (edited):
I have just received my Nexus card from Customs and Border Protection (CBP). When we cross from Washington state into Canadian San Juan Islands, it's great to be able to check in by phone, but we still having to have a customs sticker, which is just another fee. There is also a long list of stuff you can't take with you.
Nexus is the U.S. trusted traveler program, allowing me to call when entering both Canada and returning to the U.S. They can ask me to come to the customs dock, but if no one shows within 10 minutes, I am free to go. BUT, as a trusted traveler I am held to a higher standard - if they stop me and find something (booze, person on board without a Nexus card), fines and punishment are much worse. Nexus is valid for 5 years and costs $50 USD. Everyone one on board needs one - if just one person doesn't have a Nexus card, everyone has to check in at a customs port.
The customs sticker is also required to cross the border. You apply online, send $27.50 USD, and they send you a sticker that you must display. It's valid from January to December of the year you get it.
I wrote the CBP, and they told me I do not need a passport when entering the U.S. by boat. This is contrary to some of the other information I have been told.