The Centers for Disease Control and Prevention has a message for potential cruise-goers: Don’t do it.

The agency issued a COVID-19 warning last week, calling cruising a high-risk travel activity, even among the fully vaccinated. “The virus that causes COVID-19 spreads easily between people in close quarters on board ships, and the chance of getting COVID-19 on cruise ships is very high, even if you are fully vaccinated and have received a COVID-19 vaccine booster dose,” an agency advisory read.

As the highly contagious Omicron variant continues its rapid spread across the country, the agency said last week that it’s currently investigating COVID breakouts on more than 90 ships. Norwegian Cruise Line and Royal Caribbean reported positive COVID-19 cases on ships this month, and have strengthened their onboard mask policies as a result. Carnival Cruise Line also reinstated a mask policy this month.

But the warnings and high rates of infection aren’t stopping cruise-goers from getting on ships and sailing across the globe.

“CDC also says we should wear a mask everywhere we go,” Francena Lewis, who was aboard Carnival’s Vista cruise ship, told KHOU-11, a Houston news station. “But you see anybody doing that?”

Norwegian Cruise Line said it believed its guests were better protected from contracting COVID-19 than in any other general settings. Norwegian and Carnival have said they will continue on with their normal itineraries and schedules despite the CDC warning. Disney’s Wonder cruise ship and Carnival’s Vista are set to sail out of Galveston this month with thousands of passengers on board. “I believe that Carnival wouldn’t let us get on this cruise if it was that bad and that toxic. That’s my opinion on it,” said Lewis.

Cruises departed from New Orleans and Florida after the CDC warnings were issued. “I still would have gone on the cruise regardless,” Chad Stout, who disembarked from the Carnival Glory in New Orleans last week, told local news source Fox 8. “It is what it is. I’ve had COVID. I got the shot.”

Norwegian, Royal Caribbean, and Carnival all lost money in 2020 and are expected to do so again in 2021. Their stock prices fell after the CDC released their cruise guidance last week.

The Cruise Lines International Association, a group that represents the interests of the industry, expressed confusion at the announcement.

“The decision by the CDC to raise the travel level for cruise is particularly perplexing considering that cases identified on cruise ships consistently make up a very slim minority of the total population on board,” it said.