Will polar tourism sink or swim?

The sinking of the MS Explorer in Antarctica's icy waters Nov. 23 has raised concerns on several fronts, including passenger safety on cruises to the area as well as what effect the sinking -- and increasing tourism -- will have on the environment.

The 100-passenger ship was the first commercial passenger ship ever to sink in the coldest, driest, most desolate place on Earth.

A gash about the size of a fist inflicted the mortal wound on the vessel when it struck ice in waters surrounding an island chain that is part of the Antarctic Peninsula well north of the Antarctic Circle, where most cruises operate.

The 246-foot Explorer, built in Finland in 1969, was not an icebreaker and did not have a double hull. But according to its owners, G.A.P. Adventures of Toronto, it was specially reinforced to withstand blows from ice and was certified at the highest rating given by Finland and Sweden for nonicebreakers -- 1A1.

Denise Landau, executive director of the 99-member International Association of Antarctica Tour Operators (IAATO), headquartered in Basalt, Colo., said that the nonprofit organization has had a safety plan in place since its founding in 1991 and, according to Landau, it was the main reason three ships responded so swiftly to the Explorer's SOS. That plan includes maintaining a list of all vessels, their schedules and itineraries so every maritime operation knows who's where and when, and how to respond in case of an emergency.

"Everyone is overreacting" to the accident, Landau said. So far, cruise lines operating in Antarctica report no changes in plans -- or cancellations -- as a result of the sinking, which caused no loss of life.

Others are not so sanguine.

It's spring in Antarctica now, and more than 35,000 tourists are expected to visit by the end of their summer. In comparison, 6,750 tourists visited during the 1992-93 season.

The accident has renewed concern about the impact of cruise ships on the sensitive environment. It was estimated that the Explorer held as much as 48,000 gallons of marine diesel fuel when it went down, and although IAATO said that was expected to dissipate readily, the full impact on the environment of the vessel's lubricant oils, plastics and debris is still unknown.

Some cruise lines explicitly state the dangers of cruising these frigid waters. In fact, at least one line's warning is outright alarming, noting that rescue may not be possible.

Princess Cruises, which has sailed in Antarctica for four years, has two cruises planned for the 2007-2008 season on the 2,600-passenger Star Princess.

But Princess' Julie Benson pointed out that the ship cruises only in the relatively ice-free summer months of January/February and "will transit only open water and areas with limited ice floes like those we regularly encounter in Alaska and northern Europe."

Landau defended cruising in Antarctica.

"The Antarctica Treaty provides for freedom of access, and it's virtually impossible to impose limits in international waters," Landau said.