Interferance...?

Just been watching the Rip Curl boardmasters online...and in the last heat one of the riders dropped in on one of the brazilian surfers...and there was a bit of confrontation. The result of the drop in was called as interferance on the riders behalf...
Just wondering what they mean by interferance and how it effects the score of the surfers involved...does it have any repurcutions?
Just wondering what they mean by interferance and how it effects the score of the surfers involved...does it have any repurcutions?