While the most recently remembered incident of zoo enclosure cross-over is that of Harambe, this story of this ape is way different.
Rick Swope did something amazing but still highly unadvised to prevent a tragedy while on a zoo trip in 1990.
Two apes were fighting, but Jo-Jo decided it was no match for him, and started to flee the scene, but fell into the moat that goes around the enclosure and is meant to protect visitors. Chimps cannot swim, and the fall would have been proven to be fatal for Jo-Jo if it wasn’t for Swope.
Against the warnings of the zookeeper, Swope scaled a security fence and dove into the water, swimming towards Jo-Jo. You can watch the dramatic event below!