The 19-year-old was swimming with a friend just before 12.30am Monday morning.

A Queensland Police Service spokeswoman said it appeared the man had lost his footing and failed to resurface.

A mass search for the man has been operating since about 1am, with a surf rescue helicopter, the police helicopter and officers and surf lifesavers on land and sea all searching.

Police are appealing for public assistance from anyone who may have seen any trace of the man.

"We obviously hold grave concerns for him," the spokeswoman said.

Earlier: There's still no sign of a man missing off Surfers Paradise beach after almost six hours of searching.

The man was last seen entering the water at the popular tourist spot at about 12.25am Monday and police started the search close to 1am.

Water police and the rescue helicopter are involved in the search, to which police say they are dedicating "all available resources".