That website says 20 minutes. So if you're on time, the question is how long does it take to clear customs? I certainly wouldn't check bags, and I would try to sit as close as possible to the exit to beat folks to the customs line.

I have a 2 hour connection to Caulker and I've asked whether that's OK, given it's the last boat of the day. The answer I've received is "yes," but I got the impression it would have been "no" had I had only an hour to get the boat.