I picked up an I-68 in 2002 from the INS office at the Ambassador Bridge. It is a document that isn`t required from Canada, rather, it is a US document that allows u access into this country via water without checking in at customs. For example. You make a run to Belle River to fish for `skies and on your way back you are stopped by the INS when u enter american waters. If every one on board has a valid I-68 they let u go. If not, they can make u check in at customs. One of which is at the bridge and I believe the other closest one is in Algonac. Basically it is a pre check for customs. I didn`t get one in 03 because I didn`t get a canadian license. In all my years fishing StClair I have yet to see an INS boat on the water. In my opinion it is for raising $$$$$$. A terrorists isn`t gonna get one anyway.