Previous studies on contamination of swimming pool water showed that the hygienic behaviour of swimmers is the most important factor. The suggested hygienic behaviour is; having a pre-swim shower and using the toilet when nature calls. Knowing the importance of hygienic behaviour is one thing, knowing how to change hygienic behaviour is something else. A field experiment was designed to study the effectiveness of minimal interventions (short message and pictogram on poster) to increase pre-swim shower behaviour in a holiday park swimming pool. To find the best approach, signs were designed based on different ways of information processing in the human brain (psychology and communication). This study observed the pre-swim shower behaviour of over 1500 bathers during 10 different settings, including 1 baseline, 2 different informative interventions, 2 different normative interventions, two different interventions based on facilitating equipment, and 3 combinations of the most effective (informative + normative, informative + facilities end normative + facilities). The results clearly indicate that the normative approach had the strongest positive effect on pre-swim shower behaviour, with 50% more pre-swim showers taken compared to the baseline condition. Also, improvement of facilities was found to be effective in changing pre-swim shower rates, which also goes for combinations of multiple methods. The variables age, carrying belongings and parental guidance of children and teenagers also appeared to influence pre-swim shower behaviour. Outcomes of the study can be implemented in practice directly.@en