If you land in Canada, you have to notify Canada Border Services Agency (CBSA). You will be given a number you must record as proof you've done so. Upon returning to the U.S., you have to notify U.S. Customs and Border Protection (CBP) and give them that number. Nobody but the ship's master/skipper is allowed to leave the boat until those requirements are met, going in either direction. Failure to abide by the rules can result in serious consequences, amongst them having your boat and all possessions confiscated, arrest, fines, etc.
The trick is: What defines "landing?" According to the Port Huron head of U.S. CBP, "landing" consists of either going ashore
or hooking-up with a Canadian boat. Simply anchoring in Canadian waters does not constitute "landing." (
Warning: I am not a lawyer. I'm only repeating what we were told at a club meeting, where a U.S. CBP agent held a seminar.)
The documents you spoke of, there are three, are as follows: I68, NEXUS and boat registration. Boat registration is only required for boats over 30' in length. I68 and NEXUS are joint U.S./Canada programs designed to speed the process of crossing the border each way. I68 is good for one year. (I don't recall the process or what it costs.) NEXUS is good for five (5) years and costs $50. They are each per-individual programs and they only help you if everybody on the boat is participating in either the I68 or NEXUS program.
Here's the U.S. DHS site for applying for NEXUS on-line:
https://goes-app.cbp.dhs.gov/
I don't know how obtaining an I68 or boat registration is accomplished.
When you do what you're doing, are you "landing?" I don't know. But I would suspect that if you're stopping in a part of Canadian waters that's shallow enough to walk on the bottom with your head above water, as with a beach, you very well may be. I would suggest you call both the U.S. CBP office in Detroit and the CBSA and ask.
Make no mistake: The authorities,
particularly the U.S. authorities, have no sense of humour where these things are concerned.
Jim