Theory-based design for promoting positive behaviours in an urban blue space: Pre-and-post observations of a community co-created intervention in Plymouth, United Kingdom

•A pre-post behaviour observation mapping study was conducted using a co-created small-scale blue space intervention.•Post-intervention, the use of the intervention and the neighbouring non-intervention area both increased.•Post-intervention, the odds of standing, visitors being women or in a group were higher in the intervention area.•Post-intervention, the odds of viewing were higher across the site.