The Celebrity Edge cruise ship is docked in Fort Lauderdale, Florida, before it departs on June 26, 2021. - Celebrity Edge is the first major cruise ship to restart operations from a US port since the Covid-19 pandemic shutdown cruise travel. (Photo by Maria Alejandra CARDONA / AFP) (Photo by MARIA ALEJANDRA CARDONA/AFP via Getty Images)
CNN  — 

The world’s cruise ships were once titans of the oceans, raking in billions in profit as their city-sized passenger populations traveled across the globe.

But last year, many of these floating palaces became coronavirus epicenters, turned away from port after port as Covid cases rose on board and the pandemic escalated on land.