I saw the most bizarre thing the other day. I was driving across the interstate bridge from downtown Portland, and from there you can see a good ways down the river towards the industrial area. A small one or two person plane flew over the bridge and started descending rather rapidly. At first I thought it might have been a seaplane, but realized it didn't have the buoys (term?) on the landing struts. It continued descending til it was literally less than 10 feet off the water and went down the river until I couldn't see it anymore. I have no idea if this move was legal or not, but it surprised me to see a plane flying so incredibly low in city limits above a river (not lake or ocean) not near an airport. Any pilots have insight into this kind of incident?
(c)Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.