This is misleading information above. Not a very good generalization, Mark. What is true is that there are publications where you can
not touch down in water and where you are prohibited. These publications are published in the seaplane pilots association website and you must be a member to view them. It is called the water landing directory. The prohibits that have been lifted and are also added to the directory. There are not many contrast to the comment above.
As a rule of thumb, if there is no publication that says you can't land in a certain body of water then you can land there but be aware that if a problem is created (ei. noise pollution) then it may become another on the list. Be extremely friendly and cater to the surrounding neighborhoods if any are in the area. Offer them a ride so they can get a view of what it is like to fly instead of the view as "something that makes noise over my house". There are very few prohibited areas in my state. South Cali, I never looked at them.
Here is a link...
http://www.seaplanes.org/index.php?option=com_content&task=view&id=41&Itemid=68