I did some research into this ride, and I'm of the opinion that Adventureland was extremely neglectful of its operating condition and had established no procedures for a water rescue in the area where the raft overturned even though they knew rafts being stranded there after a ride stop was possible
https://medium.com/@spennydc/lack-of-maintenance-and-disregard-for-industry-recommended-safety-procedures-may-have-contributed-bfe6a22cd232