Kirsty Brown's colleagues said she was a "vibrant, dynamic individual"

Colleagues who witnessed the attack immediately launched a rescue boat to try to save her.

And although they managed to retrieve her body and begin resuscitation, the 28-year-old marine biologist could not be revived.

The Cambridge-based British Antarctic Survey (Bas), which runs Rothera, said everyone connected with the organisation was shocked by what had happened.

Bas director, Professor Chris Rapley, said: "This is tragic and shocking. My heart goes out to Kirsty's family and her colleagues at Rothera.

"Kirsty was a vibrant, dynamic individual, committed to her science and with a promising scientific career ahead of her.

"The Rothera team reacted in a highly efficient and professional manner of which we, and they, can be proud. They are, however, shaken by the loss of a colleague and will need our support."

Leopard seals are often inquisitive when they encounter humans. However, they are not generally known to attack humans unless provoked.

Bas, which has launched an investigation into the incident, has been carrying out research involving snorkelling and diving for the last 30 years.

Ms Brown, a graduate of both Royal Holloway College, University of London, and Southampton University, whose parents live in West Sussex, was with her snorkelling "buddy" when the seal pulled her underwater.

Her research project involved looking at the impact of iceberg scouring on Antarctic near-shore marine animal communities. She was a qualified and experienced scientific diver.

Medical facilities at Rothera include a surgery with emergency facilities. There is a full-time doctor at the station to deal with general health care and emergencies.

Resuscitation efforts at the base were said to have lasted an hour.