The chances of being boarded nationwide are extremely slim with about 1 in 100 boats in the coastal areas getting boarded each year. In coastal areas of Florida and the Gulf or Caribbean passages, the chances are understandably higher.
A U.S. Coast Guard Boarding:
What to expect: A uniformed CG boarding team will notify you that they are coming aboard to conduct a CG boarding. Like other law enforcement officers, they will be armed. Once on board they will conduct an initial safety inspection to identify any obvious safety hazards, and to ensure the sea worthiness of your vessel. The boarding officer will then ask to see the vessel registration or documentation, and proceed to inspect your vessel. The scope of the vessel inspection, during most boardings, is limited to determining the vessel's regulatory status (e.g. commercial, recreational, passenger, cargo, and/or fishing vessel) and checking for compliance with U.S. civil law applicable to vessels of that status. The CG may also enforce U.S. criminal law. The boarding officer will complete a Coast Guard boarding form (CG4100), and note any discrepancies.
You will get a signed copy before they depart.
Report of Boarding: When a CG boarding officer issues you a boarding report, they will either issue a yellow copy, if no discrepancies were noted, or a white copy if there were. A white copy will indicate a warning or a notice of violation. The CG boarding officer should explain the procedures to follow in each case. In any event, those procedures are written on the reverse of the form (CG4100). If you have any questions ask the CG boarding officer.
Goto: U.S. Coast Guard Boarding Policy