A cruise ship with 100 passengers aboard which sank off Antarctica last November vividly illustrates the environmental threat posed by the rising number of eco-visitors. MS Explorer spilled diesel after hitting an iceberg, damaging the continent's fragile environment. It was on a 19-day tour of Antarctica and the Falkland Islands which cost more than US$12,000 per person. Conservationists saw the accident as a wake-up call and urged restrictions on the tourist flow to the region. It is estimated that about 30,000 people will visit Antarctica to observe animals like penguins and seals this year - a four-fold increase from a decade ago. Tourism in Antarctica is currently regulated by the International Association of Antarctic Tour Operators.