Um ... yes, a few ... 199 entries in flightsim.com - a good portion of which are FS9
Jens Kristensen did Short Sandringhams, Solents, Calcuttas, and a very non-short list of more flying boats that will keep you bailing water for a very long time.
Kazu Ito did a Marlin, and a pile of funky Luftwaffe boats ...
Richard Alexander van Hien made some of the Latecore French boats, as did Alexander Belov.
Mike Stone made a PBY, as did Alphasim, Wim Regeer did some interwar German boats, Vladimir Zhyhulskiy made a Beriev, and the Schneider Trophy packages (9 if memory serves) has more flying boats than you likely ever thought possible. Not a single rubber wheel in sight for miles!
Search for flying boat as a scenery also - there's a great Hawaiian package for the Pan Am Martin boats, and my personal favourite, the Harry Levy Sunderland adventure/scenery pack. You'll fly from Scotland to the bowels of Africa never touching tarmac. The AI alone is worth the price of admission, which like most of these gems, is amazingly free with some minor installation tweaks.
The "two big" sites and THE OLD HANGAR are where you'll dig these out - I'm sure they'll give you more hours of entertainment than the average seaplane flight ...
cheers,
dl