This appears to be an improvised song that Dave and Friends played and/or teased several times over the course of the Caribbean Cruise Getaway in February 2006. The setlist originally posted on dmband.com lists two separate songs, "Off the Boat" and "Get on the Boat," as being played; however, these two songs are identical save for Dave's singing "Gotta get off the boat" during one and "Gotta get on the boat" during the other. - dmbalmanac
Gotta get off the boat
Gotta get on the boat
Back on the boat
When we first walked over here
They weren't sure we were supposed to be on the boat.
And then somebody got off the boat
And told them
They wanted us to get on the boat.
So we got on the boat