Records set at the divisive competition are not considered official because athletes are allowed to take performance-enhancing drugs. The global swimming body has condemned the event as a "circus, built on short-cuts."

As Cam McEvoy’s world record time becomes a focal point Las Vegas, swimmers say the lure of million-dollar bonuses outweighed concerns over drugs, reputation and risk.

Two-time Olympian Hunter Armstrong has pocketed $350,000 for less than 25 seconds work in Las Vegas.