I have four original plans for seaplanes. These are old plans for free flight models, all easily converted to RC. Plans are $10 each postpaid. PM if interested.

MAN Cubee, 39 in span, .049, low wing twin floats.
Aeromodeller Heinkel He 5 (S5) Hansa. Twin float, scale model, 1/2A, 38 in wing span. low wing, twin floats.
Berkley Junior Privateer, 1/2A, 36 in span, kit plan.
Hobby Helpers #654. McGovern's Monster.