Raft made by my scout troop and I using only duct tape and cardboard.
Transported to camp and home in trailer on top of all our gear.
We were quite a sight on the highway, 2 hour trip - everyone looking at us the entire time.
At camp it took 5 of us to get it on to our trailer and pull it across camp down a steep hill.
We used for a week at camp and it never sank!
Bought it home the same way and it's still intact and really to go again!
Step 1: We use large cardboard tubes, used in construction for making concrete pillars and wrapped them with duct tape.
then used cardboard cut into triangles to make the tips and wrapped in duct tape.