Marnie Hunter and Stacey Lastoe, CNN
(CNN) -- The last remaining US cruise ship in Havana Harbor, Royal Caribbean's Empress of the Seas, departed Cuba on Wednesday afternoon.
It was an abrupt end to a burgeoning market for US cruise lines, prompted by a Trump administration announcement Tuesday banning cruise travel to Cuba from the United States.
"This affects nearly 800,000 passenger bookings that are currently scheduled or already underway," according to a statement from industry group Cruise Lines International Association.
"We are disappointed that cruise lines will no longer be operating to Cuba," said Adam Goldstein, the association's chairman. "While out of our control, we are genuinely sorry for all cruise line guests who were looking forward to their previously booked itineraries to Cuba."
Cruise companies have been scrambling since the announcement to understand the implications of the policy change and adjust itineraries accordingly.
Carnival Corporation -- the parent company of Carnival Cruise Line, Holland America and Seabourn -- confirmed Wednesday that the company is no longer allowed to sail to Cuba "effective immediately."
"Currently, Carnival Corporation is sailing to Cuba on Carnival Cruise Line and Holland America Line, and Seabourn has been scheduled to begin sailing in November to Cuba. Additional details for currently booked cruises will be provided by the cruise lines," the company said in a statement.
Carnival Cruise Line offered some details on current and upcoming sailings, including a Carnival Sensation cruise currently in progress.
Guests aboard that ship will call on Cozumel, Mexico, on Thursday instead of Havana. The cruise line extended its apologies and a $100 onboard credit to those passengers.
Carnival Cruise Line is also in the process of notifying guests on upcoming sailings about their options, which include canceling affected itineraries for a full refund, remaining on affected cruises with a $100 per person onboard credit or switching to another itinerary and receiving a $50 per person onboard credit.
Royal Caribbean announced Wednesday that 2019 sailings with Cuban ports of call on Majesty of the Seas and Empress of the Seas will call on alternative ports in the Caribbean. Cruise guests will be permitted to cancel current bookings for a full refund, or maintain their bookings with a new itinerary and receive a 50% refund.
Norwegian Cruise Line said in a statement Tuesday that the company is "closely monitoring these recent developments and any resulting impact to cruise travel to Cuba. We will communicate to our guests and travel partners as additional information becomes available."
Confusion surrounding the ban is palpable among cruise companies, travel websites and passengers with tickets to Cuba.
Erica Silverstein, a senior editor at cruise review site Cruise Critic, said they are fielding questions on what the ban means for people who've paid in full or who are waiting to make final payments on planned trips to Cuba.
"It's worth noting that cruise lines are able to swap itineraries relatively quickly. We see it often during inclement weather, or in the wake of disruption in particular regions," Silverstein said.