CHEMISTRY COMMUNITY

How come we cannot do:
2 O(3) (aq) becomes 3 O(2) (g)
in the redox reaction:
O(3) (aq) + Br-(aq) becomes O(2) (g) + BrO(3)- (aq)
The solutions manual had stated the half reaction differently but why wouldn't this be correct?

Is it because of the difference in the oxygen's state? Or just because we need to include H2O and OH- into it? Thank you for your help!:)