The research project was initiated by Fina after talented American open-water swimmer Fran Crippen died during a 10km event in the United Arab Emirates in 2010.
He had won bronze medals at world championship open-water swims in 2009 and 2010.
''It was a wake-up call for everyone in elite open-water swimming,'' Prof Dave Gerrard said. Gerrard, the professor of sports medicine at the University of Otago, took up the challenge with Dr Jim Cotter, an associate professor of sport, and exercise sciences and PhD student Carl Bradford.
A research contract was drawn up by Fina with the University of Otago, which has a history of more than 130 years of biomedical research.
A side effect of the research project was to revitalise the world-class swimming flume at the School of Physical Education as a research tool.
It has given a future to the flume, which was in danger of being shut down because of a lack of use.
''We have a state-of-the-art swimming flume in Dunedin,'' Gerrard said.
The research has provided Fina with the information it needs to make open-water swimming safer.
''Our research has extend the scientific knowledge of the process.''
But the researchers issued a note of caution.
''No single number, regulation, arbitrary guideline or objective measure of environmental conditions will ever take the place of the combined vigilance of the coach and swimming officials,'' Gerrard said.
''Swimmer safety will always be a combined responsibility.''
It has been long recognised that any form of sustained physical activity will generate significant heat.
''The normal core body temperature of around 37degC rises rapidly,'' Gerrard said.
''The normal mechanisms to dissipate heat are quickly invoked to counter the rise in body temperature and the potentially serious hazards of heat stress.''
Heatstroke was more likely when body temperature was above 40degC.
The 10km open water swim has been described as the aquatic equivalent of the marathon in terms of its duration, sustained energy requirements, heat production and other physiological demands.
''An area of significant difference is the body's ability to maintain normal body temperature while immersed in water,'' Gerrard said.
''Swimmers cannot rely on the recognised physiological mechanism of cooling to reach and maintain a thermal steady state.''
An important part of the research was to find out how swimmers coped with temperatures outside the normal swimming pool temperatures that range between 20degC and 32degC.
''Questions have also been raised over the reliability of swimmers to recognise their degree of stress and level of fatigue in temperatures outside this range,'' Gerrard said. The academic literature showed that a lot had been written about the progression towards hypothermia in cold water but little meaningful research had been done that could be applied to prolonged exercise in warm water.
Twenty-four competitive swimmers and triathletes from the ages of 18 to 50 participated in the research project in the flume.
The research was funded by Fina, the International Olympic Committee's Medical Commission and the International Triathlon Union.
Open-water swimming Research findings
In more than 100 trials, no swimmer recorded a core temperature over the approved upper limit of 40degC.
No swimmer was unduly affected by the range of water and surrounding temperatures.
Core temperatures rose and subjective responses to psycho-physiological stress were recorded but they were not accompanied by any consistent changes in stroke mechanics.
Swimmers were able to reliably perceive their thermal status and make appropriate behaviour adjustments.
A five-day increase in volume training had no effect on heat tolerance or behaviour thermo-regulation, despite participants feeling sore and tired.
There was no evidence that heat conditioning in warm water gave any functional, psychological or behaviour adaptation for future events at similar temperatures.
