The activity profile in surfing has been studied by using time-motion analysis, which is a reliable method that uses detailed analysis of video recordings, along with the characterization of the internal load through heart rate (HR). The aim of this study is to characterize the activity profile of a surfing session. A surfing session, lasting 45 minutes, was filmed with a Portuguese athlete (73kg, 1.84m) who has competed at national level in which HR was recorded with a Polar optical HR sensor (“Polar Verity Sense”), placed around the arm on the exterior part, following manufacturer guidelines. Session HR, using the average, maximum and minimum values and percentages of time were used for analysis. Session HR values were: average 116bpm; maximum 138bpm and minimum 91bpm. During the session, the following HR values (average, maximum, minimum, respectively) were found for specific activities: “paddling to return to the lineup” – 116, 135, 91 bpm; “sprint paddle for the wave” – 118, 132, 106 bpm; “general paddle in the lineup” – 118, 138, 93 bpm; “stationary” – 136, 137, 91 bpm; “wave riding” – 115, 128, 106 bpm; “recovery of the surfboard” – 115, 122, 107 bpm. In conclusion, the top three activities in which the surfer spent more time were “paddling to return to the lineup” (19.53%), “general paddle in the lineup” (27,15%) and “stationary” (45,63%). For future studies, using a Global Positioning System and other physiological tests to determine HR intensity zones could provide a better understanding of the surfing modality and the training process to be adopted.