The Viking Polaris cruise ship sits on the water.
The Norwegian-flagged cruise ship Viking Polaris anchored in waters of the Atlantic Ocean in Ushuaia, southern Argentina, on December 1.
  • The Coast Guard is assisting with inquiries into four deaths on Antarctic cruise ships last year.
  • Three US citizens died in wave-related encounters while in Antarctic waters in November.
  • "This is a destination where there are increased risks when traveling," a cruise expert said.

The US Coast Guard is investigating a series of deaths and injuries of American citizens on Antarctic cruises over a two-week period last year, the agency announced earlier this month.