Some Experimental Boats made from Coroplast and other Corrugated Plastic sheets.
Several designers have played with Corrugated plastics and made some usable boats. Using this type of boatbuilding method results in ultra light boats that are easily folded and transported. Here are a few.
Because Coroplast is quite an inexpensive material, it's easy to experiment with it. Give it a try, start with cardboard models and go on to a 4x8 sheet.
Ken Simpson has produced several simple reliable and easy to build designs. He has made his folding choroplast boat plans available free. For some of his wooden boats see my take apart and folding boats page.
Applied Sciences has free plan for "45 Minute Kayak"
Link to pdf plan of an 8 ft corrugated plastic kayak. This is likely a fun inexpensive afternoon project with the kids. Minimum instructions. I would use Gorilla Tape or the Scotch heavy duty tapes for this and make sure I have a pfd on. Make a model out of cardboard first.
Too short to be an adult's boat but will easily carry a smaller human.
Corogami Dragonfly Kayak boat is a fabulous folding boat. Quite a complex folding plan but stiff and solid. I'm not sure it is still available but the design is worth looking at.
Folding Boats with No Parts coroplast boats is stiff and easy to assemble.
No Parts have designed a model of folding boat that is hugely simple to fold up and transport. I think they are designing it as an emergency/rescue boat. I don't think it is available commercially. They are using thicker coroplast. Looks like close to half inch, this makes the sheet much stiffer.
I'm cheating a bit because this is not corplast at all but it is rather a good folding boat. It has the advantage of being stiffer. It looks a bit like polycarbonate but stronger. At one point he hammers it and the boat survives. Have a look.
Tucktec folding boat
It looks like you can buy it directly from them and it is also available from Amazon.com.
Coroplast is widely used as a material for remote control miniature boats and planes. Here is a link to a Jet Boat and another link to a Jet plane
If you are interested in RC airplanes here is an introduction to building RC planes book for you. from Amazon
These 2 coroplast signs show commonly available sizes. The top sign seen in cross section, is 8mm thick. It is surprisingly stiff. To bend this would require some heating to soften the board. A similar thickness is used by the Folding Boats with no Parts.
The lower sign is 4mm thick and much more flexible. It can easily be scored and bent with no heat. Any boat made with this would require stiffening to be safe. Ken Simpson uses this for his folding boat. He adds a plywood floor and thwarts as well as side rails to stiffen the boat.
Because corrugated plastic is essentially 2 waterproof sheets with air spaces in between, any boat built of choroplast will float quite well IF THE SPACES DONT FILL UP WITH WATER. Ken seals the edges with tape and this would keep water out.
A 4 mm sheet of corrugated plastic will enclose about 11 litres of air which will support 11 Kilos. This is not quite enough to support a person standing up or even sitting but it will support you if you are lying in the boat. Make sure you have your pdf on too. If your coroplast centre fill up with water then you don't get this flotation.
This information is for general knowledge. Using non tested materials can be dangerous. If you build a coroplast boat be careful and make sure you test and use your boat in safe waters with appropriate personal flotation devices and backup help.
Coroplast is a trade name for Corrugated plastic sheet made in many colours and thicknesses. Coroplast is a US company. In other parts of the world other trade names might be better known. Examples are Plaskolite, Corplast, Coroboard, Corruboard, Polyflute, Intepro, Correx, Twinplast, Impraboard, Alylux are other tradenames. If you are looking for a local supplier Googling these alternatives might be helpful.
I have not personally tested these boats. I can't say if they are safe. These are experiments by people who like to play and design things. Be careful already!