A bit of Weird behavior I found. I don’t know why it’s occurring.
^ This is the mesh doing the boolean, procedurally set up to find the highest and lowest point of the input mesh and instance and realize some cubes.
This is obviously on the test:rubbertoy from Houdini, since Blenders Suzzane is non-manifold. But I doubt that it being from other software matters. Instead I thought maybe it’s the number of islands? The rubber toys flippers and back fins are all floating islands, not connected to the body, but they are all water tight, no holes anywhere.
I used Suzzane too, I just deleted some of the eyes and bridged the edges from the eyes and the eye sockets to make it all watertight. That seemed to work fine as you can see in the video.
And just to make sure, I used the pighead from Houdini as well, an airtight suzzane like object, had no problems there.