A wave energy generator which was launched off the south coast of New South Wales in March, has sunk in rough seas.
The 170-tonne structure had been providing electricity to the grid from 150 metres offshore at Port Kembla.
But the ABC reports it broke free from its pylons on Friday afternoon and sank on Saturday.
Early efforts to tow the barge to safety were abandoned due to rough conditions.
The Port Kembla Ports Corporation says the structure was battered against the break water.
Chief executive officer Dom Figliomeni says attempts to retrieve the barge will be made this week.
Sydney-based developer, Oceanlinx is investigating what happened.