a puffer fish under a slab with water underneath can attack the player or domesticated animals.
It doesn't seem normal that it could attack through a slab and end up hurting you or killing your pets.
I think it shouldn't be able to hurt through the slabs.
Thanks for your attention
Environment
Put your operating system (Windows 7, Windows XP, OSX) and Java version if you know it here
Linked issues
duplicates 1
Comments 2
Seems like a Duplicate of MC-126163
This issue works as intended.