Eighteen lifeguards or surfers judged surf bather drowning putative risk factors based on their experience in surf activities. Each judge rated the likelihood of a person requiring rescue in 27 scenarios in a Latin square arrangement for unique combinations of three levels for swimming ability, surf bathing experience and wave height, with replication. All factors provided unique contributions to drowning risk (p<.001). An interaction (p=.02) indicated that occasional surf bathers face a proportionally increased risk of drowning at increased wave heights relative to experienced surf bathers. Ethical approval was granted by the Monash University Standing Committee on Ethics in Research Involving Humans.