What exactly are we swimming in?

I just read this pr about the Pan Ams Champs last month. Makes you wonder just how safe that water you are diving into actually is.

OSDH Announces Results of Triathlon Illness Investigation
The Oklahoma State Department of Health (OSDH) announced today that an investigation of gastrointestinal illness reported in a recent Oklahoma City triathlon was related to exposure to water during swimming practice sessions or during the swim portion of the event.The OSDH began its investigation after receiving reports that some participants became ill following their participation in the Boathouse International Triathlon held in Oklahoma City May 16-17. State health epidemiologists queried participants through an online survey to try to determine what event or personal exposures could have led to diarrhea, vomiting and other gastrointestinal symptoms. Of the 367 participants, 218 responded to the survey and of that number, 45 met the OSDH case definition for illness, which was an acute onset of diarrhea in a 24-hour period and/or vomiting following the event. Health officials also sought stool specimens from those reporting illness.

The rest of the article can be found at http://www.ok.gov/health/Organization/Office_of_Communications/News_Releases/2009_News_Releases/OSDH_Announces_Results_of_Triathlon_Illness_Investigation.html