Ocean waves are a huge, largely unexploited energy resource, and the potential for extracting energy from waves is great. Research in this area is driven by the need to meet renewable energy targets, but it is relatively immature compared to other renewable energy technologies. This brief review introduces some device types that represent the state of the art of Oscillating Water Column (OWC) technologies, a kind of Wave Energy Converter (WEC). Unlike other works in literature, typically limited to specific aspects of WECs, in this paper will be pursued a system wide perspective, from the sea waves to the grid connection, with a particular focus on the power electronics.