The next tidal project is set to be in the Sound of Islay off the Scottish coast due to be completed in a couple of years time.
Islay tidal project
The problem is that the technology is still be worked on to get the best efficiency out of the power available in what is a very harsh environment. The outputs available are increasing for tidal machines so they are becoming a better investment.
Wave technology is very flimbsy and has smaller output capacities so isn't as financially viable as wind turbines where investors know they will get their returns.