TNT move through block once activated in bubble soul sand water

When a TNT is activated in what i call "bubble soul sand water", if there is a block just above the last water block, it can move through the block, and sometime break blocks around

(i made it with 12 dispensers in the screenshot but it can be made manually)

Video that because it's too heavy: https://www.youtube.com/watch?v=LbAedvOhQn4