His problem was caused by a deadly low sodium level in his system. He died due to hyponatremia-- lack of sodium. Hyponatremia is a metabolic condition in which there is not enough sodium in the body.

He apparently drank lots of water, but that doesn't replace the sodium that is lost from heavy sweating.

He should have balanced his drinking with water and sports drinks such as Gatorade that contain sodium and electrolytes. That being said, drinking only Gatorade type drinks to rehydrate can also cause problems.

Obviously this was an extreme case as the guy was competing in an endurance, multi-day paddling race. It's a 260 mile, nonstop race.

However, as hot as it gets down here, everyone should take precautions to rehydrate properly when sweating heavily.

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Sodium

When you perspire, your body loses about 900 to 1400 milligrams of sodium per liter of sweat (Shirreffs & Maughan, Exercise and Sport Sciences Reviews 28: 27-32, 2000). Sodium is an important component of blood; having sufficient sodium in the blood helps keep a sufficient volume of water in the blood. Ingestion of sodium during exercise should also help prevent hyponatremia, a condition in which the concentration of sodium in the blood becomes dangerously low (Convertino et al., Medicine and Science in Sports and Exercise 28: i-vii, 1996; Vrijens & Rehrer, Journal of Applied Physiology 86: 1847-51, 1999; Medicine and Science in Sports and Exercise 32: 2130-45, 2000; Speedy et al., Emergency Medicine 13: 17-27, 2001).

The sodium content of Gatorade is about 450 milligrams per liter; for Powerade, it is 225 mg/L. Thus Gatorade does a somewhat better job of replacing the sodium lost in sweat.

Thanks Chris!
That is some good information and something I wasn't aware of.
What's the salt content of beer? Just kidding!
It's a shame but drewb will probably attempt to contradict everything you said.