this is a hard problem for a permenant fix. for a quick day of fishing, think tape...! R*d Gr**n would smile just thinking about it, but it would work. even the M*th B*sters showed it that it worked. good duct tape is okay, the armed forces green water resistant tape is much better, and the plumbers metalic works better too. the last 2 have a much better glue that holds up well to water while the metalic takes a bit more abuse. think probable fixes needed on your patch, so take spare tape with you. also test any tape you are going to use - not all of it will take water and most need to be applied to a dry surface.
hmmm, would an inflatable boat rub bumper piece work? there is a place on line that sells repair and upgrade kits for inflatables. these rub bumpers are designed to be added to give protection from rocks and docks. made of a flexable material, they offer several glues. maybe this would work and help protect this obviously vulnerable area. just a thought.