The Great Barrier Reef Ocean Observing System is deploying sensor networks on seven sites along the Great Barrier Reef in north-eastern Australia. The project has a strong data focus and is actively developing data management systems to manage the data collected. A data schema based on deployments has been developed with a deployment hierarchy of platforms (e.g. buoys, moorings), instruments such as loggers and the sensors themselves. Supporting schema entities include an equipment register that holds the details of the equipment deployed, service history and calibration entities and a sensor relationship entity that holds details of how individual sensors relate to each other. Metadata is collected using the Australian Marine Community Profile of ISO-19115 using the GeoNetwork open-source software. Using the parent-child relationship in ISO-19115 one parent record per platform deployment is created, a child record for each instrument deployed on that platform and a grand-child record for each sensor deployed on the instrument. A framework for quality control has been developed that at the lowest level uses the IOC/IODE set of quality control flags and a simple rules based system to deliver a 'Level-0' quality controlled product. Higher levels are also defined where manual corrections and complex processing are applied to create higher level data products. The Open GIS Consortium Sensor Web Enablement framework has been chosen for data exchange and representation. SensorML is used to describe the sensor systems while Observation and Measurement ML is being investigated for the data itself. The usability of these XML standards is an issue as many are complex and the supporting tools and software are still under development.