The first thing you need to build a big paper boat is the desire to build one :)
Its kind of a hard and not that easy task. You must be patience and maybe need some help to build one. By yourself its kind of tiring and its better if you build it with someone. Also more fun.
But the result will totally pay off.

Step 1: Materials

-Big roll of paper. I happened to get two big rolls and I just taped them together to make a bigger one.
-Scissors
-Celo tape

Step 2: Preparation of the Dimensions of the Paper

To make a paper boat one of the sides of the paper must be larger than the other. It depends on how big/tall you want the body of the boat to be.

Step 3: Building the Paper Boat

-Fold the sheet in half. (This step is quite essy although the big paper sheet is quite heavy, folding it in half it is not a problem, later on the foldings get harder).
-Fold the corners to the middle like in the photo. triangle shape with space ln the bottom (That space will determine the size of the body of the boat).
-Fold flaps at the bottom on both sides.
-Pop out the middle to make a hat shape (Here is where it gets hard and not easy to manipulate. Be careful not to break the paper. If it breaks, do not worry, just use celo tape).
-Open the hat shape out until it forms a square. tuck corners of one flap under the other.
-Fold up the bottom flaps pn both sides (triangle shape).
-Pull out the middle of the triangle to form a square.
-Press the shape flat.
-Open out from the bottom to assemble your boat shape.

Step 4: Ta-da!

You now have a big paper boat. Dont worry if in the first try it does not turn like you thought. Just be patience and it will be ok. After lots of effort and after sweating like a lot (you can skip gym this day), you will get your boat.

Tips!!! If it is too big, it kinds of starts folding back!! Use celo type to keep it on shape. And build near the place you want it to be (if not you will need kind of a huge car to transport it).