There is growing interest in surfing as a recreational activity that may facilitate skill development and improved mental health. However, there remains uncertainty regarding the causal processes through which surfing may improve psychological well-being. With the aim to guide future research, we review potential mechanisms that may underpin the psychotherapeutic effects of surfing. A range of plausible factors are identified, including exercise, water immersion, exposure to sunlight, transcendent experiences, reductions in rumination and the satisfaction of basic psychological needs. Further research is needed to clarify the effectiveness of surfing-based therapies and to establish the relative contributions of the causal mechanisms at play.