I suggest a chap to Steve Powell in EGAB with reference to the small flying boat(s) mentioned. Steve runs the Amphibious Flying Club and as a seaplane instructor is first class. He has some experience in with one of the types mentioned.
For what it's worth, I fly 150hours a year in Ireland on straight floats. All I can say regarding a potential seaplane purchase is look at what works in Canada and AK. I've flown a Grumman Goose here in IRL with the man I consider the guru of waterflying.... 16,000 hours on the water - no accidents. There are places on this big blue and green planet where people hold water flying as a religion and seek to learn from their experience.
When you mix aeroplanes and water - Its very easy to have an expensive and embarrasing mistake.....Somethin akin to a good episode of "The Last of the Summer Wine" would be a common occurance!!