The Taylor Swift-themed cruise from Florida to the Bahamas went from happy to sad Tuesday ... as a 66-year-old woman fell overboard and is now missing.
A rep for the U.S. Coast Guard tells TMZ ... the Royal Caribbean cruise ship filled with Taylor's "Swifties" left the Port of Miami Monday and was about 17 miles north of Nassau in the Bahamas when tragedy struck Tuesday night.
According to the spokesperson ... the woman tumbled off the ship called Allure of the Seas, plunging into the ocean at about 9:40 PM.
The Royal Bahamas Defense Force, assisted by the U.S. Coast Guard, responded and conducted search and rescue efforts, using helicopters and airplanes.
But, so far, the woman has not been found and is considered missing.
The cruise was supposed to be a fun get-together attended by Taylor's most ardent fans to celebrate the pop star's career.
But, it's now turned into a nightmare as rescuers comb the waters to find the missing woman. It's unclear if she was part of the Swifties contingent or a separate group. It should be noted that Taylor herself is not involved in the cruise.
As you know ... TMZ broke the story Monday about the Taylor-themed bash, posting a bunch of photos showing the Swifties having a blast onboard the ship.
A Royal Caribbean spokesperson tells TMZ ... "Our crew immediately launched a search and rescue effort and is working with local authorities. We are also providing support and assistance to the guest's family during this difficult time. To respect the privacy of our guest’s family, we have no additional details to share."