I blow up a balloon, tie it off, and take it to the bottom of the swimming pool. What will happen to the balloon and the air inside it

A blown balloon is tied at the bottom of the swimming pool. The balloon will only get narrower and the air inside of the balloon will get thicker. As we go down inside the swimming pool the pressure of water increases and this causes the air inside the balloon to compress and become dense. This causes the balloon size getting smaller.

The above are the result of Pressure and volume effect.