While playing in a world created the previous preview today, the screen would go black and pressing any relative key combination wouldn't quit or escape the process. When running on macOS, Minecraft runs in a Java session that required me going into Terminal to force quit the process.

When this happened, I was in a boat on my way to find hidden treasure. When I rejoined the game, I started on the shore near where I hopped in the boat, and when I got close to where the game crashed before, it crashed a second time.

Following that crash, I force quit the Java process again, quit the launcher, and restarted my Mac. On restart, I launched Minecraft, loaded the world, and figured I'd head off in some other direction. About 10-15 minutes into playing, the same thing happened: The screen went black and I had to force quit the Java process in Terminal.

Please see the attached crashlog, which describes this as "Exception in server tick loop".