Steven P. McNicoll wrote:
wrote in message
ps.com...

From a practical matter, does the seaplane have any duty to radio that
they're taking off?


No.



What about any traffic flying in back of the seaplane, in blind spots?


That traffic must see and avoid the seaplane.



And ORD arr. and dep. traffic appears lower than 3000'
near the Chicago shore.


It isn't.

If you want to see seaplanes in a busy harbour, go to Vancouver. In the
January "Canadian Aviator", an article describes how Vancouver Harbour
ATC manages floatplanes, helicopters, freighters and cruise ships from
the worlds tallest control tower. The magazine is at
http://www.canadianaviatormagazine.com/ but the latest issue is not up
yet.

John Halpenny