Two cruise passengers onboard a Quark Expeditions voyage in Antarctica have died after their Zodiac overturned in a tragic accident.

The guests onboard the World Explorer’s were on a Zodiac which overturned near shore, Quark Expeditions said in a statement to Seatrade Cruise News.

“A Zodiac boat carrying six passengers and two expedition staff overturned near shore, tragically resulting in two fatalities,”Quark said.

“The weather conditions were light winds and smooth sea state, and indications are the accident was caused by a breaking wave. The other four passengers and two staff are recovering under the care and observation of our doctors and medical staff on board,” the statement continued.