has found himself in hot water again ... this time, the Olympian has been busted for violating the U.S. Anti-Doping Agency's rules ... and he basically snitched on himself.
Lochte -- who was part of the Team USA swim team's infamous gas station incident at the 2016 Games in Rio -- wasn't popped for using a banned drug ... but for receiving an IV treatment illegally.
But, here's the crazy part -- Lochte reportedly led USADA right to the investigation by posting a pic of the IV treatment on Instagram. The post was later deleted.