This is the time for nesting and the swan is probably protecting a clutch. So, no matter what you do, the swan is going to keep you from going into that area with his cygnets (baby swans). Give it about a month and his hormones will calm down because the cygnets will be a little bigger and he will be a little less protective.

Should you scare him or he tries to fly at you, he could get hurt or so scared that he does not go back to the nest which could possibly cost his mate and the cygnets their lives. The Regal Swan