A cruise ship is docked at harbour after turning back due to positive coronavirus disease (COVID-19) case on board, in Singapore July 14, 2021. REUTERS/Chen Lin

A cruise ship is docked at harbour after turning back due to positive coronavirus disease (COVID-19) case on board, in Singapore July 14, 2021. REUTERS/Chen Lin

Environmental activists protest to demand an end to cruise ships docking at the Port of Valencia, Spain, June 19, 2021. REUTERS/Eva Manez

Environmental activists hold a banner reading "Stop cruises" as they protest to demand an end to cruise ships docking at the Port of Valencia, Spain, June 19, 2021. REUTERS/Eva Manez

Environmental activists hold a banner reading "Stop cruises" as they protest to demand an end to cruise ships docking at the Port of Valencia, Spain, June 19, 2021. REUTERS/Eva Manez

Environmental activists protest to demand an end to cruise ships docking at the Port of Valencia, Spain, June 19, 2021. Banners read "La Malvarrosa a neighbourhood fighting for its dignity" and "Less port, more public services". REUTERS/Eva Manez

Environmental activists protest to demand an end to cruise ships docking at the Port of Valencia, Spain, June 19, 2021. REUTERS/Eva Manez

Passengers of the Costa Luminosa cruise ship wearing protective face masks make their way at the port of the island of Corfu, Greece, May 18, 2021. REUTERS/Adonis Skordilis

Passengers wearing protective face masks disembark from the Costa Luminosa cruise ship at the port of the island of Corfu, Greece, May 18, 2021. REUTERS/Adonis Skordilis

The Costa Luminosa cruise ship prepares to moor at the port of the island of Corfu, Greece, May 18, 2021. REUTERS/Adonis Skordilis

A crew member of the Celestyal Experience cruise ship wearing a protective face mask is seen on the bridge of the ship at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

Sunbeds are piled up at the empty pool deck of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

Armchairs are stored at an entertainment area of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A view of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

An entertainment area of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A red and white cordon tape blocks the entrance of the casino area of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

The bar at the empty pool deck of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

The empty pool deck of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A bar area of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A crew member of the Celestyal Experience cruise ship wearing a protective face mask opens the door of a cabin at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A dog rests at the entrance of Cruise Terminal A "Miaoulis" of the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A view of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A restaurant of the Celestyal Experience cruise ship, which is moored at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

A hand-shaped placard reading "Ciao" is seen on the bridge of the Celestyal Experience cruise ship at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

The mooring ropes of the Celestyal Experience cruise ship at the port of Piraeus, Greece, January 29, 2021. Picture taken January 29, 2021. REUTERS/Alkis Konstantinidis

Royal Caribbean's Quantum of the Seas is moored at the Marina Bay Cruise Centre after a passenger was tested positive onboard for the coronavirus disease (COVID-19), in Singapore December 9, 2020. Picture taken December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship is moored at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Passengers leave Marina Bay Cruise Center after disembarking from the Royal Caribbean's Quantum of the Seas cruise ship, which is moored after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Passengers leave Marina Bay Cruise Center after disembarking from the Royal Caribbean's Quantum of the Seas cruise ship, which is moored after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship is moored at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

A fisherman holds a fishing rod in front of Royal Caribbean's Quantum of the Seas cruise ship, whose passengers wait to disembark after the ship was moored at Marina Bay Cruise Center, following a tested positive for coronavirus disease (COVID-19) passenger during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Passengers wait to disembark from the Royal Caribbean's Quantum of the Seas cruise ship, which is moored at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship is moored at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship is moored at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Medical personnel helps a passenger onboard an ambulance as other passengers wait at the Royal Caribbean's Quantum of the Seas cruise ship, which docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

An ambulance leaves the Marina Bay Cruise Center, where the Royal Caribbean's Quantum of the Seas cruise ship docks after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Medical personnel helps a passenger onboard an ambulance as other passengers wait at the Royal Caribbean's Quantum of the Seas cruise ship, which docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Personnel in PPE stand on a doorway as Royal Caribbean's Quantum of the Seas cruise ship docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Personnel in PPE stand on a passageway as Royal Caribbean's Quantum of the Seas cruise ship docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Passengers wait to disembark Royal Caribbean's Quantum of the Seas cruise ship, docked at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Passengers wait to disembark Royal Caribbean's Quantum of the Seas cruise ship, docked at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Personnel wearing PPE look on from the cruise terminal of Marina Bay Cruise Center where Royal Caribbean's Quantum of the Seas cruise ship is docked, after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

The balconies of the Royal Caribbean's Quantum of the Seas cruise ship, docked at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Passengers look from their balconies of the Royal Caribbean's Quantum of the Seas cruise ship, docked at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

Royal Caribbean's Quantum of the Seas cruise ship docks at Marina Bay Cruise Center after a passenger tested positive for coronavirus disease (COVID-19) during a cruise to nowhere, in Singapore, December 9, 2020. REUTERS/Edgar Su

A view of the media event at the Dream Cruises' "World Dream" cruise ship, Singapore's first cruise to nowhere since the coronavirus pandemic shut down the cruise industry, in Singapore November 6, 2020. REUTERS/Travis Teo

Self check-in kiosks for passengers are seen at the Dream Cruises' "World Dream" cruise ship, Singapore's first cruise to nowhere since the coronavirus pandemic shut down the cruise industry, in Singapore November 6, 2020. REUTERS/Travis Teo

Self check-in area for passengers is seen at the Dream Cruises' "World Dream" cruise ship, Singapore's first cruise to nowhere since the coronavirus pandemic shut down the cruise industry, in Singapore November 6, 2020. REUTERS/Travis Teo

People walk near the coronavirus disease (COVID-19) swabbing stations for passengers at the Dream Cruises' "World Dream" cruise ship, Singapore's first cruise to nowhere since the coronavirus pandemic shut down the cruise industry, in Singapore November 6, 2020. REUTERS/Travis Teo

Mein Schiff 6 cruise ship is moored at the dock of Piraeus after some of the crew tested positive for the coronavirus disease (COVID-19), in Piraeus Greece, September 29, 2020 REUTERS/Costas Baltas

Health Ministry officials enter the Mein Schiff 6 cruise ship moored at the dock of Piraeus after some of the crew members tested positive for the coronavirus disease (COVID-19), in Piraeus, Greece, September 29, 2020 REUTERS/Costas Baltas

Passengers stand at the balconies of the Mein Schiff 6 cruise ship moored at the dock of Piraeus after some of the crew members tested positive for the coronavirus disease (COVID-19), in Piraeus, Greece, September 29, 2020 REUTERS/Costas Baltas TPX IMAGES OF THE DAY

Crew members sanitise a table as the Mein Schiff 6 cruise ship is moored at the dock of Piraeus after some of the crew members tested positive for the coronavirus disease (COVID-19), in Piraeus, Greece, September 29, 2020 REUTERS/Costas Baltas

Passengers stand at the balconies of the Mein Schiff 6 cruise ship moored at the dock of Piraeus after some of the crew members tested positive for the coronavirus disease (COVID-19), in Piraeus, Greece, September 29, 2020 REUTERS/Costas Baltas

Mein Schiff 6 cruise ship is moored at the dock of Piraeus after some of the crew tested positive for the coronavirus disease (COVID-19), in Piraeus Greece, September 29, 2020 REUTERS/Costas Baltas

A passenger stands at the balcony of the Mein Schiff 6 cruise ship moored at the dock of Piraeus after some of the crew members tested positive for the coronavirus disease (COVID-19), in Piraeus, Greece, September 29, 2020 REUTERS/Costas Baltas

A woman walks next to the Mein Schiff 6 cruise ship moored at the dock of Piraeus after some of the crew members tested positive for the coronavirus disease (COVID-19), in Piraeus, Greece, September 29, 2020 REUTERS/Costas Baltas