Is a new form of renewable energy going to be underwater waves?

The United Kingdom; known for it's unique weather and the Queen,

Illustration of  the Turbines underwater.
Source: CNN

may not be able to create large amounts of renewable energy from the sun or from a wind farm, but there may be a new for of renewable energy. However, being a collection of islands, it does have thousands of miles of coastline which contains tides going up to 18 mph. An upside to using water instead of air, with the increased density compared that of air, it requires less surface area to create a spin with the blade, it will require less space per wheel. Another useful benefit is the turbines are underwater, and would not block the beautiful view outside into the ocean.