There is currently great interest in monitoring the microbiological quality of bathing waters and ensuring the safety of users. The European Bathing Water Directive 2006/7/EC which came into place in 2011 sets strict new standards for the classification of bathing waters. Ability to rapidly test microbiological quality of bathing waters is a powerful tool for meeting water quality standards and guidelines, risk assessment and management systems. Real-time and on-line monitoring are key factors for consideration in current method developments for continuous indicator organism assessment to meet early warning requirements and water safety plans. The aim of this work is to address the need for tests capable of rapid on-site and in-situ assessment of microbiological water quality. To achieve an active management of bathing areas and to reduce the risk associated with the presence of faecal pollution, such tests are essential. In the 1st part of this thesis, commercial in-situ sensors are used to collect continuous high frequency water quality data for a period of 7 months in Dublin Port. These data are used to identify pollution hot-spots at the site and coupled with data collected from discrete samples it is shown that continuous monitoring can be used as a decision support tool. In the 2nd part, the thesis looks at developing a rationale for monitoring water for biological contamination and follows by establishing a proposed sensor technology based on a bacterial marker enzyme and fluorescence optical detection. A novel protocol for the recovery and detection of faecal pollution indicator bacteria, E. coli, using β-glucuronidase (GUS) activity is developed. The developed protocol involves two main steps: sample preparation and GUS activity measurement and has a time–toresult of less than 75 min.