Hi All,
Some of the obvious places, countries, etc. have already been mentioned... but one overlooked:
Lake Como has it own aquatic aerodrome with extensive fleet; based just down the road from Lugarno and Milan I would imagine it's a great place to combine seaplanes with beautiful Italian and Swiss mountain flying in the region and without having to cross the globe to do it! And from what I understand they do let you go "SOLO."
http://www.aeroclubcomo.com/En/Fleet.asp
Good luck & let us know how it goes whichever route you take.
EG
www.navex.aero