: Ive got a huge hole in the rear of my plastic ocean kayak due to a
: fire.

Rotomolded? No matter. You can repair it with an epoxy called G/Flex by West Systems. You have to have some backer material. If you can go to a kayak dealer and pick up some scrap kayak material of the same color, you can do a pretty good job of making a visually acceptable repair. West Systems has some info on their site. Here is a link:

http://www.westsystem.com/ss/gluing-plastic-with-g-flex-epoxy/

Here is a video from West Systems that might give you a chuckle. It shows what you can do with this stuff:

http://www.westsystem.com/ss/g-flex-torture-demo/

By the way, you can make your repair "prettier" than the repair they did. I think they were trying to emphasize their material too much.

You can also "weld" some polyethylene materials. Some you can't. You need a plastic welding setup. You can make an almost invisible weld IF the material is weldable. I have welded some polyethylene and some acted like they were some sort of thermoset material. I tried to weld a Jackson 4 Fun and was unsuccessful. I had to use G/flex.