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?

Question

The balloon will get bigger and the air inside the balloon will be less dense (molecules move further apart).
The balloon will get smaller and the air inside the balloon will be more dense (molecules move closer together).
The balloon will get bigger and the air inside the balloon will be more dense.
The balloon will get smaller and the air inside the balloon will be less dense.

Answer 1

The balloon will get smaller and the air inside the balloon will be more dense (molecules move closer together). This is due to the increase in pressure at deeper depths in the swimming pool, which compresses the air inside the balloon.