The Oyster was a hydro-electric wave energy device that used the motion of ocean waves to generate electricity. It was made up of a Power Connector Frame (PCF), which is bolted to the seabed, and a Power Capture Unit (PCU). The PCU is a hinged buoyant flap that moves back and forth with movement of the waves. The movement of the flap drives two hydraulic pistons that feed high-pressured water to an onshore hydro-electric turbine, which drives a generator to make electricity. Oyster was stationed at the European Marine Energy Centre (EMEC) at its Billia Croo site in Orkney, Scotland until the company ceased trading in 2015.

Aquamarine Power installed Oyster at the EMEC in August 2009. On 20 November 2009, Oyster was officially launched and connected to the National Grid (UK) by the First Minister of Scotland, Alex Salmond.

Development work was started to build a more efficient and powerful second-generation device, Oyster 2.

Oyster was developed by Edinburgh-based Aquamarine Power, a company that focuses on wave energy. The concept originated from research at Queen's University, Belfast, led by professor Trevor Whittaker, Head of the Wave Power Research Centre at Queen's. Aquamarine Power also teamed up with Renewable Technology Ventures Ltd (STVL), a subsidiary of Scottish and Southern Energy (SEE), to fund the Oyster project. Aquamarine Power was able to secure a £6.3m investment from Scottish Enterprise. In addition, Scottish Enterprises awarded Aquamarine Power a £3.15 million grant from the Wave and Tidal Energy: Research, Development and Demonstration Support fund (WATERS). Aquamarine Power also received £1.5m from Sigma Capital Group plc. Altogether, Aquamarine Power was able to raise £11 million to stage this project.

In June 2009, Aquamarine Power signed a £2.5 million contract with Fugro Seacore to install the Oyster device at the European Marine Energy Centre test site at Billia Croo. Oyster was installed 400 metres offshore, west of the Orkney mainland, in 12 metre-deep water. Oyster was installed in August 2009; however it was officially launched on 20 November 2009 by the First Minister of Scotland, Alex Salmond. That same day, Oyster was connected the National Grid (UK) and began generating electricity.

Aquamarine Power hoped to commercialize Oyster and signed an agreement with Scottish and Southern Energy to develop up to 1000MW of wave farms by 2020. However, the test programme ended in 2015, when the company failed to find investors and ceased trading.

Oyster harnessed the energy of near-shore ocean waves; it was designed to operate in water 10 to 12 metres deep. The Oyster is made up of a Power Connector Frame (PCF) and a Power Capture Unit (PCU). The 36-ton PCF is bolted to the seabed by 1-by-4 meter concrete piles that are drilled 14 metres deep into the seabed. The PCF requires careful and accurate positioning and leveling to compensate for the uneven, rocky seabed. The PCU is a 200-ton, 18-by-12-by-4 metre buoyant flap that is hinged to the PCF. In order to lower the PCU into the water to hinge it to the PCF, 120 tons of seawater must be pumped into ballast tanks within the PCU to provide sufficient negative buoyancy to aid its descent into the water. The PCU is almost entirely submerged underwater; only 2 metres of the device poke above the water. The PCU sways back and forth with the movement of the waves, and this movement of the flap drives two hydraulic pistons that pump high-pressured water through three sub-sea pipeline to an onshore hydro-electric water turbine. The turbine then drives a 315 kW electrical generator, which converts the wave energy into electricity.

The European Marine Energy Centre classifies Oyster as an Oscillating Wave Surge Converter: