: Is exterior grade ply good enough for a S+G or do I need to buy marine grade?
: I cant find any marine suppliers around here likely....kirk

There's a rash of boat building among Texas kayak fishermen going on these days, they're mostly building pirogue type boats, but a couple JEM sit-on-tops too. So far they've all been built with el cheapo plywood, some have used polyester resin from Lowe's, et al, though most are using epoxy. All projects have been successful and a lot of them are now being fished out of.

Having reported all that, I'll now cast my vote for Dave Gentry as giving the best advice.