International Journal of Exercise Science 14(6): 1388-1399, 2021. Surfing is a popular sport globally which is performed in varied environmental conditions. With limited research in the field exploring hydration, monitoring the effect of surfing on subject hydration is warranted. The purpose of this study was to determine the relationship between surfing intensity and hydration status. A total of ten recreational male surfers were recruited for this study where hydration status was assessed pre-and post-surf session by measures of body mass (BM) and urine specific gravity (USG). Intensity of the surf session was quantified by Global Positioning Systems and Heart Rate monitoring. Subjects surfed for two hours and covered an average distance of 4974.18 ± 542.62 m, with an average speed of 2.48 ± 0.27 km/h and peak speed of 31.86 ± 3.51 km/h. A statistically significant decrease in absolute and relative BM was observed (0.70 ± 0.4 kg, p \u3c 0.05 & 0.86 ± 0.54%, p \u3c 0.001, respectively). No statistically significant correlation was found between variables (total distance paddled and relative BM, r = 0.432, p = 0.245; average HR and relative BM change, r = -.246, p = 0.595). Total distance paddled combined with average HR significantly predicted relative body mass change (F(2,3) = 29.362, p = 0.011, adjusted R2 = 95.1%). The results demonstrate that a 2-hour recreational surfing session, in temperate environmental conditions, without neoprene garments resulted in minimal BM changes and no changes in USG. Surfers who paddle a greater distance at a higher average HR sustained greater BM changes
