I recently started a server using Snapshot 18w20a, but I remember this happening when testing out early snapshots as well. Whenever I walk there's a blurry line that seems to start maybe 25% of the way up from the bottom of the screen. It runs down the screen from there as I walk then eventually shows up again and repeats. This doesn't happen in 1.12.2. Currently vanilla with default textures. I've tried changing all the settings and nothing seems to help. Any ideas?