A Gull That Thinks It's a Dipper

I was by the River Exe hoping to photograph Dippers. One did fly past, but there were none in the river. When this gull, I think it's a Juvenile Herring Gull, but if you know better let me know. Was flying past and dropped what looks like a slice of cheese, the gull soon lost interest in the cheese and started diving in the river before flying off. No Dippers but very Dipper like activity.