HDPE plastics (what the kayak is made of) can now be glued. Or should I say that there are now glues for HDPE plastics. The only problem I have come across is that you need to order the product, as I have yet to find a supplire local. Here is a little how to on it:
http://www.ehow.com/how_8641794_glue-hdpe.html
Here is a supplier, they also include a load/weight pounds per square inch chart based on material HDPE is bonded to:
http://www.innerduct.com/products/hdpe_glue.php
The important key here is proper preparation.
Best of luck!