Need to post that over at Hobie forum. Here.

Several threads there about nicks and cracks in rotomolded. Usually nothing can be done or used to permanently repair a nick or crack. That looks pretty bad to me. The only question is whether it might be in a place that is structurally solid and where it will not grow. If so, you could keep the crack filled with caulk to at least keep water out. I doubt it, but that question is for the tech reps.