The inflatable boat has passed its sea trials!
Bought an Intex Explorer 400 for a whopping $40 at Wal-Mart. Includes two surprisingly sturdy plastic oars and a hand pump. This is "4 person" boat but, like tents, cut that in half for adults. This will hold two average size people pretty comfortably.
The boat feels very light (as would be expected), but also fairly well made. The 30 gauge PVC feels substantial. I was a little nervous boarding the boat because we have riprap on our pond banks, but the rock did not puncture the boat.
This boat has three chambers to inflate. I used the hand pump because my electric one is apparently broken. Took about 15 minutes and some not insignificant elbow grease to get it pumped up with the hand pump. I left it inflated overnight to see how well it holds air. Does not appear to have an appreciable amount overnight.
The hardest part of the whole process was cutting out a piece of plywood to fit the bottom. Even that wasn't too tough and I got a pretty good fit. I've seen people wrap the plywood with outdoor carpet, but for now I just wrapped the edges with duct tape to avoid any punctures.
I'd say the plywood bottom is essential unless you plan to just use the boat as a big pool toy. If you want to sit up in the boat, an adult is going to need the hard bottom.
On the water, the boat feels stable. It is rated up to about 700 pounds, but I seriously doubt it can manage that. No problem for the 250 pounds between myself and my child.
All in all, I am extremely satisfied with my purchase. This is going to be a very good, inexpensive solution for installing and periodically servicing our floating fountain, and then stowing away when not in use.
Tomorrow I install the fountain. I think I'll start a new thread for that.