Adventure holidays, which often involve white-water rafting, are becoming increasingly popular, according to people in the Irish travel industry.
White-water rafting is popular because of the adrenalin rush it produces. Participants enjoy the unpredictability of being at the mercy of a fast-flowing river.
Described as one of the most physically demanding activities, white-water rafting is mainly undertaken in Nepal, Australia, New Zealand and the Pyrenees.
The trip taken down the Salzach river in the Austrian Alps by the three Irish people was particularly difficult, with melting snows transforming many parts of the river into a raging torrent.
Mr Richard Schiefer, a police spokesman in the Salzburg region, says "very few boats or rafts use the Salzach river" because it is so hazardous and large rocks can lie submerged beneath the raging water and boats can be upturned.
The most popular white-water rafting sites are often the most dangerous. One of the best known is on the Kali Gandak river in Nepal, where participants pass through a gorge known as the Goddess of Death. Three years ago an 18-year-old London woman drowned there.
Ms Ann Maxwell, of Maxwell Travel in Dublin, which specialises in adventure holidays, says anyone who goes white-water rafting should be a good swimmer and very fit. Accidents have been rare over recent years, but the huge travel insurance needed reflects the risks involved.
"It is not just young people who like to go on these expeditions. A lot of older people also enjoy the experience and see it as a kind of challenge," she says.
The three Irish people who died are understood to have been on a package holiday with Air Tours, a British tour operator. A spokeswoman for the company says the Irish customers booked their white-water rafting separately.