No... it was NOT being operated on floats...
Word is that the pilot felt that something was wrong with the rudder/vertical stabilizer... vibration/shudder... appeared to be getting worse and decided to make a forced landing... I don't know if the forced landing was intended to be into the river or things got out of hand and the a/c just ended up there... at least one of the pilots had considerable time on the twotter...
I'm not drawing any conclusions from this..