Great Britain has a lot to win from its all-surrounding waters. And green energy company Tidal Lagoon Power knows that. They’re planning to build a 10 kilometers-long sea wall from Newport to Cardiff to create a artificial lagoon. At high tide the water can stream in via turbines in the wall. The lagoon is then closed until low tide, when it is opened again to let the water stream out via the turbines. The company claims it could generate enough energy to power Wales. The project would cost around 6 billion British pounds (8.3 billion euros). Governement has already said it supports the idea, although negotiations over subsidies over a pilot project in Swansea have yet to start. Consumer charity Citizens Advice has warned that the project is a “appalling value for money”. It would indeed be the most expensive green energy project in Great Britain so far. Tidal Lagoon Power says it will only be expensive in the first thirty years when they have to pay constructions bills and turn a profit, but afterwards the generated energy would become very cheap.