The male lifeguard, a New Zealand national, and the woman are believed to have gone to look at a cave which is only accessible at low tide.

The search was launched when they failed to return several hours later as the tide rose. The cave at Bedruthan Steps is near Mawgan Porth.

A RNAS Culdrose helicopter and three lifeboats are involved in the search.

An RNLI spokeswoman said: "We have no idea what happened or where they are, and on that basis the search was launched."

Falmouth Coastguard said there was a big swell and surf in the area with moderate winds creating rough conditions.