You may need to be documented to get the waiver, but I'm not sure you need to
be doc'd
to do 6-pak style charters.

You can bareboat a foreign hull, but a crewed charter falls under the Jones
act.

Interesting note, as I remeber the Jones act it only prohibits using a foreign
hull to transit between two US ports. I'm not a maritime attorney, (and it
wouldn't hurt to consult one), but I think you can get away with a foreign hull
by departing and returning to the same port, with no intervening stops.

A sight-seeing run along the waterfront would seem to be OK.

Getting around the Jones act is no big deal. The general procedure is to make a
"campaign contribution" to a member of congress from your district, and request
that an exemption be read into the Congressional Record from the floor of
Congress. I guess that a couple of times a year they tag all those Jones act
exemptions in the record onto some other bill that's being passed, or maybe it
can handled as an administrative detail without even coming to vote. After you
pay off the congressperson and the request goes into the Confressional Record,
I'm a bit confused about the mechanics of the actual exemption.