I spawned next to an underwater temple and nearby was a mushroom biome.Then on either side of the mushroom biome was terrain that was glitching out in the water,bedrock and floating water and gravel,None of it was able to be walked on though.You just fell through(forgot to put in video).Video of what happened:https://www.youtube.com/watch?v=T8J0PeZ3nMM&feature=youtu.be