Olympic kite surfer Bruno Lobo -- who just competed at the Paris Games in August -- heroically saved a drowning swimmer last week ... and the dramatic rescue was all captured on video.
Lobo posted the footage to his Instagram page over the weekend ... explaining to his thousands of followers the scene played out on Jan. 10 -- as he was testing some new gear during a surf sesh off a coast in Brazil.
View this post on Instagram
The vid shows as Lobo was making his way through the waves .