Navy sailor lost off Tongan beach

The search has resumed for a Royal Australian Navy sailor who went missing and presumed drowned at a beach in Tonga.

Defence in Australia said the sailor, whose name has not been released, was a crew member aboard the Anzac frigate HMAS Warramunga.

HMAS Warramunga was conducting a scheduled Port Visit to Tonga's capital, Nuku'alofa, at the time of Wednesday's incident.

"The Royal Australian Navy regrets to advise that a member of the ship's company of HMAS Warramunga is missing presumed drowned whilst swimming in Tonga," defence said in a statement.

"At approximately 10:42 hrs today, a ship's officer notified senior authorities that a fellow crew member had possibly drowned at a beach on the western side of Tonga."

Defence said the ship's Seahawk helicopter was launched in an attempt to locate the missing sailor in the South Pacific.

The search continued until dark on Wednesday without success and resumed at "first light" on Thursday morning with support from the Tongan Defence Services.

Defence said a full investigation would be conducted.

The sailor's family has been contacted and will be provided support by Navy and the Defence Community Organisation.

- AAP