Hello!
When Quark, Yung's better caves and Biomes O plenty are installed on a Terraforged world, mega caves from the Quark mod appear so near to the surface that it creates big holes in water and in the terrain. In think it's from the fact that we can change the height of the worlds with terraforged. I thought it was a yung's better caves problem, but the autor said me it comes from Quark. So here are some screenshot and you will see, it's problematic:

You're better off just turning them off to be honest.