The incident occurred in the beach resort of Pantai Cenang, Langkawi in January when the woman opted to take an evening dip together with her family.
“It took five-six seconds, then she fell unconscious,” her husband told the newspaper.
Despite several attempts by relatives and ambulance personnel to revive the woman, she never regained consciousness.
According to Swedish marine biologist Lars Henroth, the woman was probably stung by a so-called box jellyfish, named for their cube-shaped medusae. It is a small, transparent creature which is known to carry a deadly sting.
“A heart attack is the most common reason for death when you are stung. It often occurs swiftly.”
According to the marine biology centre in nearby Phuket the box jellyfish has become more common in recent years in the waters off Malaysia and Thailand – popular winter destinations for hordes of Swedish tourists.
The centre issued an official warning last winter when an unusual number of the deadly jellyfish were found off the coast.