A tidal energy turbine in Co Down has been given the environmental all-clear, the developers have said.
SeaGen in Strangford Lough has had no major impact on the marine life with no changes in the population of seals or porpoises.
There have been "small scale" shifts in the behaviour and distribution of the creatures to avoid the turbines, the owners Marine Current Turbines Ltd said. The seabed surrounding the machine's foundations has recovered since it was installed in 2008.
SeaGen can generate enough power for 1,500 homes.
Environment Minister Alex Attwood said: "Marine Current Turbines has proved that the power of the seas can be harnessed in harmony with marine life.
"The results of their work will give everyone greater confidence in realising the economic and environmental benefits that tidal and wave energy can offer to Northern Ireland, elsewhere in the UK and Ireland as well as other parts of the world."
SeaGen works like an underwater windmill, with the rotors driven by tidal currents rather than the wind. Its operation has been limited to daylight hours but these restrictions have been lifted.
The Royal Haskoning report was produced by an environmental consultancy with an independent science group.
No major impact has been detected on the environment and there have been no changes in the abundance of seals or porpoises attributed to SeaGen, they are continuing to swim past the machine without hindrance.
The owners said: "The only changes observed after three years of operation of SeaGen have been relatively small scale changes in the behaviour and distribution of seals and harbour porpoises, which suggests a minor degree of local avoidance of SeaGen."