An all-star collaboration of jam band artists paid tribute to David Bowie on a cruise ship that was quite literally rocking back and forth in the Atlantic this week. Under the moniker 'Oh, You Pretty Things,' and led by Ron Johnson, the group featured the relatively reclusive Jon Fishman (Phish), Al Schnier (moe.), Dan Lebowitz (A.L.O.), Jeff Austin (Yonder Mountain String Band), Robert Walter (Greyboy Allstars), among others. And, of course, for an adventure called Jam Cruise, you can always expect plenty of unannounced guests and sit-ins.

Sure enough, the core group was joined at times by Ivan Neville, Grace Potter and Michael Franti, who surprised even the other musicians when he jumped onstage towards the end of 'Let's Dance' for a freestyle rap that eventually brought the impromptu jam back around to the chorus. The focus on David Bowie played into the cruise's ''80s Night' theme, which had many passengers dressed up in leg warmers or short shorts, and even a very psyched Ziggy Stardust.

"It's very much in the spirit of Jam Cruise that this whole thing came together," Schnier tells Spinner. "We still have a surplus of songs. We still have six or seven songs that are ready to go."

Some passengers who literally walked in on it were treated to a live rehearsal several days earlier in the ship's Beverly Hill's Bar, which served as the cruise's epicenter for impromptu jamming throughout the voyage.