TU35/CU23/1.26/Patch 5, TU46/CU36/1.39/Patch 15, TU47/CU37/1.40/Patch 16, TU48/CU38/1.41/Patch 17
Edit: Added image and video of a simple setup to reproduce on TU48/CU38/1.41/Patch 17 ...
You only need to lay two squares size of two chunks (hitting as much chunks with water) Y254 with water on Y255 and the game will freeze destroying the save when autosave is enabled. Added Image and short movie of crash upon loading. There is nothing else then a layout of chunks with wool in this world. And a grass floor. The game crashes first then when reloading it keeps crashing.
Sorry for the bad quality video https://youtu.be/IaQ15hXrxxA. Had to record via my cellphone as the console crashes to dashboard.
Summary: Trowing water and removing it freezes console and makes world unloadable.. Keeps crashing..
Edit: Trowing large amounts of lava the same way freezes console as well
I was working on a mob farm when the console froze and the world was unable to be loaded. It loads and then crashes the console to dashboard. After testing it was caused by the falling water I had while building the mobfarm. Tried multiple times when there is a large amount of falling water from height the console freezes and the save when loaded freezes again and again, making the world unplayable, this could be abused by other players as a way to break someones world!
By having even less falling water then illustrated in the video the console freezes. The autosave point if loaded keeps the console going to dashboard so the world becomes unloadable. Just a couple of seconds and the game crashes again. Tested in multiple worlds all over ocean. Don't know if ocean biome makes a difference.
To recreate: Go to sea biome (not sure if it will influence result) then pillar up to world limit (as in video) make something to drop a lot of water from remove rapidly using for example sponges. The game will freeze the autosave will have a point with dropping water. Making it load and freeze the console again and again.
Result: world unusable. Keeps freezing also after loading and rebooting console.
Note: The video is a seperate recording (not the actual mobfarm) from one of the test if this is what caused the world to freeze, this new world ended up unplayable as well, loading and keeps freezing.