Some scouts, my son included, have built a collaspeable kayak out of plywood and heavy canvas.Contact cement was used to adhere the canvas to the 1/2 inch plywood. On Previous kayaks efforts, all that was done to make them "sea worthy" was to prime inside and out and then paint with 100% acrylic paint. The leaders are planning to use them in seawater as well as fresh water.

My first question is this sufficient water proofing? What kind of primer should be used? Oil or latex. I was planning to use a an Oil based primer suited for a latex top coat.

I thought about using some bondo to transition the fabric edges to the wood for a nicer appearance. I've not used bondo before, is it flexible enough to resist cracking chiping or would there be a better material for this pupose.

Any insights would be appreciated, especially if it can help prevent a bad judgement call on painting approach.