As I was flying around, I noticed on the side of the islands that the Mega Lake's water isn't fully contained. Just a random block update needs to occur before the water starts spilling out from the lakes into the void which probably not what you want. The uncontained water is not always on chunk edges so it probably isn't a problem with chunk boundaries but maybe the actual containment code.

Honestly I kinda like the weird water generation, it adds to the odd end feeling of the megalake grove.

congratulations for finding a megalake that has water, because all the times I've found this biome I didn't find even one block of water, wich is ironic considering the biome's name.

and since all the times I've found a megalake it didn't had water I've maintained the english name when I did the pt_br translation because I wasn't sure if it was actually supposed to be a lake biome or not.

Looks like there's a cutoff for the structure that is caused by a different problem than the above issue. Very odd