The two WaveRunners collided, resulting in injuries to Poindexter, which caused his death.
Poindexter was a space shuttle commander and pilot for NASA. He spent a total of 28 days in space. He was also a captain in the U.S. Navy.
According to the NASA article NASA Extends Sympathy to Poindeter Family on Death of Former Astronaut, "Poindexter, a U.S. Navy captain, commanded the STS-131 space shuttle Discovery mission to the International Space Station in 2010, delivering more than 13,000 pounds of hardware and equipment. He was the pilot for shuttle Atlantis' STS-122 mission that delivered and installed the European Space Agency's Columbus laboratory on the station in 2008."
NASA Associate Administrator for Education and former astronaut Leland Melvin said of Poindexter: "Alan and I joined the astronaut corps in 1998 and flew together on STS-122, which was truly an incredible experience. He was a passionate, caring and selfless individual who will be missed by all."
Peggy Whitson, chief of the Astronaut Office at NASA's Johnson Space Center in Houston, Texas, also stated, "We in the astronaut family have lost not only a dear friend, but also a patriot of the United States. He proudly served his country for 26 years as a fighter pilot, test pilot, astronaut and commander of a space shuttle. I am proud to have both flown in space and worked with him for so many years. Dex will be deeply missed by those of us at Johnson and the entire NASA family."
For more on this story, please read the Reuters article " UPDATE 1-Former U.S. astronaut Poindexter dies in watercraft accident"
The NASA biography of Poindexter is found at "Alan G. Poindexter (Captain, USN); NASA Astronaut (FORMER)"