A former Royal Australian Navy frigate has been scuttled off the coast of Sydney despite fierce opposition from environmentalists and an inopportune visit by a pod of dolphins

Hundreds of people watched this morning as HMAS Adelaide slipped beneath the waves off Avoca Beach on the New South Wales central coast in Australia to begin her new life as an artificial reef.

Adelaide hit the headlines in January 1997 when she rescued round-the-world sailor Peter Bullimore after his yacht Exide Challenger capsized in the Southern Ocean. The 4100-tonne frigate was built in the US in 1980 at a cost of around $285 million and served in the Middle East in the wake of the Iraq war.

Adelaide was decommissioned in January 2008 and although it had originally been planned to sink her in March 2010 for use as a dive site, the project was placed on hold after environmentalist groups appealed to the Administrative Appeals Tribunal.

Despite the rescheduling of the scuttling date to today, protesters had threatened to halt the sinking using other measures and they very nearly got their wish when a pod of dolphins made its way inside the exclusion zone, delaying proceedings by over an hour.

SEE BBC FOOTAGE of the ceremony to mark to occasion.