I feel like the middle of the story, where Olavo sees the burnt crew, is underdeveloped; his reaction just doesn't make sense to me. Olavo's pulling the gun on Carmo also doesn't make complete sense to me. I like a lot of the imagery at the start and end, and although some of the language can be considered as a little clunky, I like the quality of the writing overall.
I also feel like you overused "technologically advanced" quite a bit, but on the bright side, I only see a few language errors.
Is the Masasula River inspired by something specifc?