Tidal lagoons: the power of the future?
Experts say the government should support big plans to build the world's first tidal lagoons, here in the UK.
Tidal lagoons are a way of creating renewable energy, much like wind turbines and solar panels. They use the movement of the sea to help create power.
The first lagoon would be built in Swansea but the aim could be to build five more off the coasts of Cardiff, Newport, Bridgwater Bay, Colwyn Bay and West Cumbria.
But are there any worries? And how much would it cost?
Watch the video to find out more...