A man sparked a major rescue operation in Richmond this morning when he crawled inside the Church Street Bridge and couldn't get out.

The daredevil, in his 20s, luckily had a mobile phone with him and, after two hours trapped inside, called triple-0 at 4am.

However he was unable to tell emergency services exactly which bridge he was inside, sparking a two-hour hunt to find him.

As the man's mobile phone battery drained, his rescuers asked him to start whistling so they could try to pinpoint his location.