A shark has been filmed in the shallows at at Byron Bay, just below an oblivious group of surfers.

American traveller Derik Broshar filmed the video from an elevated position on the beach, after spotting the shark swimming in relatively shallow water among the surfers.

Mr Broshar told The Northern Star newspaper in northern New South Wales that other beachgoers had tried to warn the surfer, but it was so windy that the surfer wouldn’t have heard the warnings.

Mr Broshar said the shark swam around the surfers for around 90 seconds and left the area once the surfer went over it with its board.

He and other spectators were unable to identify the shark but later heard that surfers started exiting the water after having seen it swim near them.

The video has gone viral with more than 65,000 views by mid-morning on Thursday.

Watch the shark swimming among the surfers