I might be in the minority, but it would actually be cool to swim through the Paradise Pier lagoon as part of a triathlon. How many people can say: "I swam in the DCA lagoon!" ... legally, too.
At least I know one of my "million dreams" would come true at a Disney park if given that opportunity.
Couldn't one assume the event organizers and Disney have already thought about health and safety concerns regarding the water and lagoon's bottom before approving event logistics?