Once a warship that came to the rescue of asylum seekers and doomed yachtsmen, the epic life of HMAS Adelaide will not be forgotten as it is transformed into a haunting underwater haven for marine life, divers say.

A pod of dolphins delayed the scuttling for almost 90 minutes this morning, after more than a year of battles between the NSW government and environmentalists over whether to turn it into a dive wreck off Avoca Beach on the central coast.

Down she goes ... HMAS Adelaide is scuttled. Credit:Nick Moir

At 11.50am a flare was let off and the decommissioned warship quickly sank about 30 metres.