Drowning is the third leading cause of injury-related deaths worldwide and is thought to be a leading cause of death during times of flood. Activities such as driving into, walking near, or engaging in recreational activities near or in floodwater are commonly reported as preceding drowning. Reports have shown that, in Australia, around 53% of flood-related drowning deaths and 55% of all river flood-related unintentional drowning deaths were the result of driving through floodwaters. This study was conducted in two phases: an intervention development phase, and an intervention evaluation phase. The intervention evaluation phase utilised a randomised controlled trial design in which participants were randomised into one of two experimental conditions: (1) education about the risks of driving through floodwater; or, (2) education about the risks of driving through floodwater plus a theory-based behaviour change intervention using planning and implementation imagery exercises. Outcomes were measured at baseline, immediately post-intervention, and at a follow-up one month later. The intervention was delivered, and outcomes were measured, within an online survey. The effect of the intervention on the outcomes was assessed using a series of mixed-model ANCOVAs.