Water management is an important part of monitoring the natural environment and includes monitoring water quality of both coastal and inland marine locations. This covers the detection of pollution and monitoring the development of harmful algal blooms as well as coastal features and wave patterns. For many years water managers relied on field measurements for coastal monitoring and water quality evaluation. This type of sampling is quite limited on both temporal and spatial scales and is ineffective for capturing dynamic marine events, essential for increased knowledge and better decision making. It also involves costly, time and labour-intensive on-site sampling and data collection. The introduction of new policies such as the EU Water Framework Directive has increased pressure on governments to adopt new methods for continuous monitoring of all water bodies. In recent years, the use of in-situ wireless sensor networks (WSNs) for marine environmental monitoring has been developing to allow continuous real-time monitoring of the marine environment at greater temporal and spatial resolutions. WSNs have brought about great advantages and increased opportunities for environmental monitoring. The WSN concept envisages a world of ubiquitous sensing through large scale deployments of self-sustaining WSNs linked to digital communications, continuously monitoring our environment and detecting and reporting changes in its quality. However there are still several challenges remaining in the area of in-situ wireless sensor networks in order to realise this vision. Among these is the issue of data reliability and the need for a sensor network that adapts to changes in the availability and reliability of its own sensors, as it monitors an already changing environment. We are developing a reputation and trust based event detection system for environmental monitoring which incorporates alternative sensing modalities such as visual sensors (e.g. digital cameras and satellite sensing) and context information alongside an in-situ WSN. This can help to overcome some of the availability and reliability issues and essentially leads to a smarter, and more reliable event detection system for environmental monitoring.