ChunkSnapshot.getBlockType(x,y,z) will return an incorrect Material type for a specific location. It seems to be off by one in the y coordinate.

What I'm trying to do is scan a chunk starting at y = 60 until I find air blocks which are 1 block above water blocks, so that I can store a set of block changes to go ahead and make back on the main thread later. The idea here is to simulate a 1 block sea level rise in a chunk.

From what i've read ChunkSnapshot is meant for plugins like dynmap where an off by one in the Y coordinate isn't a big deal.

I've attached the log file from my testing. The true sea level is indeed at y=62, and notice that the chunk snapshot method returns that y=62 for the entire chunk is AIR, when it is not.

Since the plugin I'm testing which recreates this issue is not quite available yet, I attached the two source files which I've been using to test. These wont be usable in-game without a bit of other stuff, but it gives you an idea for what I'm trying to do.