What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration ?

Terrestrial organisms take oxygen from the oxygen-rich atmosphere where the oxygen content is quite high whereas aquatic organisms use oxygen dissolved in water which is very low as compared to the amount in the atmosphere. Since air dissolved in water has quite low concentration of oxygen, the rate of breathing is much faster in aquatic organisms to obtain as much oxygen as possible than terrestrial organisms and thus, terrestrial organisms spend less energy than aquatic organisms for respiration.