Drew Brees took more hits on Kelly Slater's surf wave machine than he does on an NFL Sunday ... saying learning to ride the waves from the surfing legend caused him to get "absolutely thrashed."
It all went down recently when the Saints quarterback took a private plane up from San Diego to Slater's wave park in Lemoore, CA ... and took on some of Kelly's epic man-made waves.
Brees couldn't ride the water for more than a few seconds ... with Slater estimating the QB fell on eight or 10 waves "back to back to back.