Sorry, Ed. Guess I assumed you were familiar with Laddie's designs. Pic attached. 22.5" wingspan, 22-24 oz RTF. The Astro 020 is a brushless, souped up speed 400, basically.
The 100% version of this is 46-60 glow powered, spans 45" or so, and weighs about 5.5 pounds. (It's a follow on to the old Northstar, which you may remember.)

It is possible to keep water out of seaplanes- I do it routinely, but if your opinion is that cooling of battery, ESC and motor is critical, I'm going to put a couple holes in the top deck so I can route air over the battery and the ESC. I can do the same thing for the motor, as there is a gap between it and the left and right sides of my nacelle, so I could mount scoops there and let the cooling air go out the back, as it is open at this point.

I had two of these propulsion units in a Jim Ryan P-38, and one of them just died. I think it may be because I had no provision for cooling. Lasted a long time, though, probably because I used to cruise around at less than half throttle. I think I did this because, looking at the Astro instructions, there is no mention of cooling. Too long ago to really remember, though.