Chapter 5 - Section 5.3 - The Simple Gas Laws: Boyle’s Law, Charles’s Law and Avogadro’s Law - Chemistry in Your Day - Page 205: 1

Volume of the balloon will decrease to 0.83 L and the air flows from the submerged balloon to the balloon on surface, because Volume if the submerged balloon decreases hence the air is pushed to the balloon on the surface.

P1 = 1.0 atm, V1 = 2.5 L, V2 = ?, P2 = 3.0 atm P1V1 = P2V2 1 x 2.5 = 3.0 x V2 V2 = 2.5/ 3.0 = 0.833