My first boat I ever built. Best for kids Originaly built in 2010 by my brother and I to explore the small pond at the end of the street.Total construction takes arond 1 hour with very little skill needed.Very simple construction requiring basic tools and materials to build. Can be built for free or little cost.
Note: Build and operate at own risk. I am not responsible for any harm or injury caused by building or operating boat.Life jacket recommended.

Materials:
(2) 2x2x4 feet
(2) 4 foot landscaping timbers
(2) 2x4x4 feet
Duct Tape
3" Screws
55 Gallon Plastic Barrel
Counterweight ex. barbell weight

Tools:
Drill & Drill Bits
Jigsaw & wood/plastic blades
Measuring Tape
Saw to cut wood

Step 1: Seal and Cut the Barrel

First, if your barrel has caps on the top and have holes in them like my barrel you need to seal them. Caulk the cap where the hole is.
Next cut the barrel. I don't have any actual pictures but do have a Google SketchUp Model. Trace in the bottom of the barrel like shown a opening based on your size. Cut the hole big enough to get in and out of but not farther than half the length of the barrel. Drill a hole in the middle of your traced opening for the jigsaw to start cutting. Than with the jigsaw cut out the traced opening. If you have rough edges sand them smooth with sandpaper.

Step 2: Build the Frame

Lay the landscaping timber parrallel to each other. Lay the 2x4s across at the ends like shown to form a 4'x4' square. Screw with 2 to 3 screws at each corner.

Step 3: Barrel Mount

Next lay the 2x2s on top of the 2x4s ach 1 foot from the end of the 2x4s. Screw on with 2 screws.

Step 4: Attach Barrel to Frame

You may need another person to do this. Lay the barrel in between the 2x2s. Make sure it is centered. Then duct tape around the barrel and 2x2s going around 2-3 times. Do this at front, middle and rear of barrel.

Step 5: Finished Product

Now your finished. Put your counterweight in your boat to balance it fore and aft. Make sure your seals are good and enjoy the water. Eventually a seat was added to compensate for height.