No, I haven't made this yet--working on the idea while collecting the kitty-litter buckets. The idea is to use the buckets as the flotation base beneath an easily-moved raft, which will be used as an observation deck for the children in our wildlife observation classes. I'm open to critiques of the idea, and especially open to suggestions that would make it more light-weight! My preference is to make as much of it as possible out of repurposed materials and salvage.
Step 1: Prep the Buckets
I'm collecting 20 kitty-litter buckets of the same size and brand (have five so far). First, I'll sand the exterior to remove the labels and prep for painting. Then I'll fill each bucket with sealed, empty plastic bottles. If any one bucket springs a leak, the bottles will serve as air-pockets to maintain flotation. Finally, I'll run a bead of silicone-sealant along the lip of each bucket, close it tightly, let the silicone dry, and then finish the bucket off with a wrap of duct-tape around the rim, to protect the silicone-seal.
Step 2: Build a Frame
Next, I'll build a frame around the buckets. I didn't draw this, but I think lashing PVC and/or CPVC along the slots on the bottom of the buckets, and in-between the buckets, will give it good cohesion and allow for both flexibility and strength. The buckets will need to be able to flex lightly with waves and minor impacts, but also maintain a stable shape. Finally, around the top edge of the buckets, I'll build the frame for the observation deck out of treated lumber.
Step 3: Build a Deck
The decking could be made of simple 1" planks. I'm thinking about using 2" pink insulation foam, covered with a 1/2" of plywood to protect the foam from dents. The exterior of the buckets that would be exposed to sunlight will be painted with a UV-protective paint. At this point, the lower framework holding the bucket-bottoms could be lashed / wired / ??? to the rest of the raft.