Pufferfish Swims Through Trapdoor

How to do:

1. Make 1 block hole.
2. Put any slab in hole on the bottom.
3. Put a trapdoor on top.
4. Put a Bucket of Pufferfish on the SLAB. (NOT THE TRAPDOOR!!!!)!.
5. Close the trapdoor. 
6. Waterlog the trapdoor.
7. Watch your pufferfish swim through the trapdoor!