I know the Alum bay area very well from boating and flying around there. I have seen planes dipping down toward the water (like 20ft) and then going off again. I thought it looked quite cool actually.
To be honest with you now I think that unless this guy was really coming close to people in their boats then he was just having a laugh and you straight and level flyers who are afraid to get a kick out of flying like that should keep to yourselves.
If he was coming THAT close why did no one get his reg.?