Answer- The given statement is true
Explanation-
The atoms that do not participate in compound formation or free oxygen atoms are present inside water which is much more than what is present in air. This oxygen is dissolved in water.
The oxygen molecule is attached to hydrogen for forming water does not count. Because it is in compound form the only oxygen considered here is the tree oxygen atoms present inside water which sustain the aquatic life and also it is more than the oxygen present in air.