A company has been granted government permission to search a large section of the Isle of Man seabed for gas and oil.
Manx-based firm Crogga have been granted three years to conduct seismic surveys of a 266 sq km (165 sq mile) section of seabed off the east coast.
Crogga said natural gas from the Manx seabed has the "potential to power the island for hundreds of years" and to provide "energy security".
The Isle of Man Green Party said it was "deeply concerned".
The island does not have its own energy supply and imports natural gas from Europe.
The Manx government owns about 4,000 sq km (1,500 sq miles) of the seabed, which stretches 12 miles into the Irish Sea from its coastline.
It now hopes advances it technology may make drilling a "more viable prospect".
Crogga said it planned to begin seismic surveys in Spring 2019, using sound pulses to build a picture of the seabed.
Further government consent would be required before drilling could take place.
Crogga's chief executive Diccen Sargent said: "We believe in a bright future for the Isle of Man as it transitions away from energy dependency on other nations."
However, the Green Party believes the testing would result in "damage and degradation to surrounding ecosystems on the seabed".
A party spokesman said the plans were also "focusing investment away from renewable energies".
Crogga was awarded a licence following a two-month bidding process in 2017.