The SmartBay Observatory in Galway Bay is an underwater observatory which uses cameras, probes and sensors to permit continuous and remote live underwater monitoring. It was installed in 2015 on the seafloor 1.5km off the coast of Spiddal, Co. Galway, Ireland at a depth of 20-25m. Underwater observatories allow ocean researchers unique real-time access to monitor ongoing changes in the marine environment. The SmartBay Observatory is an important contribution by Ireland to the growing global network of real-time data capture systems deployed in the ocean. Data relating to the marine environment at the SmartBay Observatory site is transferred in real-time through a fibre optic telecommunications cable to the Marine Institute headquarters and then made publicly available on the internet. This includes a live video stream, the depth of the observatory node, the water temperature and salinity, and estimates of the chlorophyll and turbidity levels in the water which give an indication of the volume of phytoplankton and other particles, such as sediment, in the water. This dataset comprises a summary of numerical data collected from instruments and sensors on the observatory averaged out over a period of a day. The data includes temperature, conductivity, pressure, salinity, sound velocity, oxygen concentration, chlorophyll concentration, turbidity, water velocity and sound level measurements of the seawater. Suggested Citation: Marine Institute. (2026) SmartBay Observatory Combined Sensor Dataset - 1 day average (August 2015 - Present) [Data set]. Marine Institute, Ireland. doi: https://doi.org/10.20393/0E29627F-00BD-4AC6-90F6-00A3C42FF467