Check your render distance, if it's low, then the chunks might just be unloaded. The lighting in minecraft isn't distributed in chunks; the lighting in this "bug" IS defined by the chunks (the squares on the top are chunks, but the faded bottom in the correct lighting for underwater areas. In other words, if the lighting was really incorrect, then the bottom part of the slit would be sqaurish too.
Still hasn't been fixed😑. Confirmed for 0.13.1 iPhone 5s iOS 9.2
Check your render distance, if it's low, then the chunks might just be unloaded. The lighting in minecraft isn't distributed in chunks; the lighting in this "bug" IS defined by the chunks (the squares on the top are chunks, but the faded bottom in the correct lighting for underwater areas. In other words, if the lighting was really incorrect, then the bottom part of the slit would be sqaurish too.
Need to describe a way to reproduce. Please add.
Confirmed for 0.13.1 on iPhone 5s iOS 9.2