The president fun fly  makes a good waterplane, here are a few examples, Just ensure it is well sealed with vaseline along the wing seat. Above is mine (now deceased) and left are 2 friends planes.

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A collection of mine (top right) and friends cougars on floats, This makes a highly aerobatic and manoeuvrable float plane, The top 2 are powered with  OS 46 la's giving more than enough power to prop hang,  bottom right is massively overpowered with a OS46fx. Here is an ariel video taken from my cougar.

A collection of cubs, left mine, acquired as a wreckage and rebuilt had bomb doors built in to drop a small yacht and other floating  payloads into the lake (this may not have been a scale feature) initially powered with a super tiger .45, but altered to a 60 shortly before it crashed, not sure why. the extensive wreckage was cremated.

Above is a friends flair cub powered by an irvine .40 i am currently restoring one of these as a replacment for mine.

Right A larger cub powered by a.72 engine.

Left a slightly scaled down Kingfisher I test flew this plane for its previous owner and it flew ok except for some rather sloppy linkages that were subsequently fixed. Its new owner as depicted in the boat has tried several different engines and set ups and as yet has not managed to get it off the water. it was rather windier when i flew it not sure what will happen to it. Rather a shame as it is such a nice aircraft. This plane has now been modified as a twin with 2 OS 46 la's, the test flight ended in a sudden flat spin presumably due to an engine cut, i shall try again with smaller pitch props and some out thrust on the engines.

Below is Misty usually present at the waterplane meets searching for somone with a sandwich. Dosn't actually fly.

Below is a Black Horse Twister Which  makes a nice waterplane.

The magnatilla above and below  makes an excellent waterplane powered with a .40 engine. Flies just as well as a water plane as it does as a land plane. Also seems to float and keep dry quite well if it turns over when sealed with vaseline.

Left is a Eric smith design sea hawk kept light due to the built up wing, sadly badly damaged in a mid air collision  since the photo was taken. Currently under repair.