The aim of the study was to compare the physiological responses to deep water running (DWR) compared with treadmill running (TMR) in male international volleyball players. We compared the maximum, recovery and resting heart rates, maximum blood lactate and ratings of perceived exertion between DWR and standard laboratory TMR test. The maximum heart rate (HRmax) was 14.9 bpm lower in water than on land (p = 0.001, 95% confidence interval, 7.74-22.06). The recovery HR at three minutes was 16.4 bpm lower in water (p = 0.012, CI 95%, 4.57-28.23). The differences in the maximum HR and the three-minute recovery HR likely reflected a cardiovascular response mediated by immersion in water. The maximum blood lactate and the ratings of perceived exertion suggested that both tests were undertaken at same effort levels. Before prescribing exercise intensity a water specific test should be performed.