The SmartBay Observatory in Galway Bay is an important contribution by Ireland to the growing global network of real-time data capture systems deployed within the ocean. Installed on the seafloor 1.5km off the coast of Spiddal, the observatory uses cameras, probes and sensors to permit continuous and remote live underwater monitoring. Data relating to the marine environment at the site is transferred in real-time from the SmartBay Observatory through a fibre optic telecommunications cable to the Marine Institute headquarters and then made publicly available on the internet. This dataset comprises of processed data that has been collected from the SmartBay Observatory site using a Nortek Signature 500 Acoustic Doppler Current Profiler (ADCP) (formerly a Teledyne RDI Workhorse Broadband 600KHz – see history below), which is used to measure water current velocities in the seawater above the observatory. The ADCP is mounted approximately two metres above the seabed, looking up towards the sea surface. Data are collected every minute for 1.0m depth segments or “bins” from approximately 1 metre above the instrument to the surface. This dataset comprises of the processed CSV data files containing the velocity measurements. Practical uses of this dataset include but are not limited to scientists, researchers and marine technologists involved in the area of Physical Oceanography. This is a continuously updating dataset and includes data collected using a now retired sensor. The timeline of sensor use is as follows: Oct 2015 – Nov 2021 - Teledyne RDI Workhorse Broadband 600KHz Dec 2024 – present - Nortek Signature 500