When you immediatly place down a bed in water, they hitbox of the bed or water shows 2 full blocks.
STEPS TO REPRODUCE :
1. Obtain a bed
2. Find water
3. Place the bed in water
4. See that the Hitbox was 2 full blocks for half a second
EXPECTED RESULTS :
The hitbox should be 2 half blocks instead of full blocks.
Attached video only shows the bed being broken and does not actually demonstrate the bug.