In 14w11b, tnt destroys blocks even when in water. I tested it in older versions, and it didn't destroy any blocks while in water

Put the summary of the bug you're having here
Tnt destroys blocks even though it was in water

What I expected to happen was...:
It wouldn't destroy any blocks

What actually happened was...:
it caused a lot of damage to the machine

Steps to Reproduce:
1. dig a 3x3 hole, and fill with water
2. put tnt around the middle source
3. activate all tnt at the same time