When I generate a brand new 1.13 world I usually easily get 60+ FPS.

But, as soon as ocean biomes start generating, particularly it seems if I enter the biome or if the biome is in range of spawn chunks, the memory usage starts to spike and the ms/tick rate quickly rises to 1000-3000 or more ms per tick.

The game stops responding to inputs reliably and I usually end up in a 1 FPS or worse situation. While in this situation I've had the game crash twice so far, but unfortunately did not have the crash reporting enabled at the time. I have now turned it on but coincidentally haven't crashed since doing so.

Oddly, I played in Pre-Release 5 on the same computer while coincidentally also opened to LAN playing with my daughter on a world for hours over the course of a couple days doing nothing but exploring oceans for treasures with almost no lag issues at all. But with the release version, the moment any oceans generate I'm in a slide-show.

The console logs errors like:
Can't keep up! Is the server overloaded? Running 12635ms or 252 ticks behind

Quitting to menus and reloading the world is insufficient to clear the issue.

Quitting Minecraft entirely and then reloading the world seems to resolve the problem for a minute or two, but the lag spikes start very quickly if you are in range of an ocean.

I did search for existing issues before creating this, but none seemed to match the Minecraft platform, version, and symptoms properly. Apologies if I missed one.