Where can you purchase this? I am in Alabama.

You should be able to purchase it from your local lumber store. Perhaps, Lowe's or Home Depot would carry it.

Good Fishing,

There are lots of places, but most local hardware or building supply places can order it for you.  If you can wait until they place their regular orders, some will let you avoid paying the shipping.  Also, I talked at some length about this with a boat builder who told me that years ago, there was a big difference between marine and construction woods, mainly having to do with the adhesives used.  He told me this is no longer the case, and that the glues are all the same with the differences having to do with voids in the inner layers, and the quality of both sides.  Regular sheathing is usually AC, where it is grade A on one side, and C on the other.  Marine woods will be AA, but if you are painting, AB will be good, and MUCH cheaper.  Do your research before you spend a lot of money.  BTW, I've used regular plywood, covered it with polyurethane, and had very good results.  And it won't matter what you use, if you don't seal it, it will rot.  Remember that after you drill holes, and seal them well.

WELCOME!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

That's expensive wood. If you're building a deck on your boat , you can go a lot cheaper as long as you seal the wood.

Regular sheathing plywood is usually know as CDX and made from pine , not very strong and relatively heavy compared to fir  ie. AB, AC.  If you have a cabinet supply near you check with them on some five or seven ply exterior grade. The more plys the smaller the voids and the the stronger and more stable the plywood.

Travlin Man is right about the sheathing being CDX.  He must build stuff for a living.  I was in Lowe's today looking at wood to make some cabinets for my garage.  The sheathing stuff is usually 3 or 4 ply and is not what I used.  It was about $6 more, but I used some 5 ply 5/8 BC for my decks.  There are 2 trusses under it made of aluminum angle and they are about 2' apart, with 3 pieces between the trusses.  It looks kind of like this [|] with no breaks.  and there is a hatch in part of it.  I weigh 225 easily, and can jump up and down on it, and I've jumped off of the dock onto it many times.  No flex.  The problem with wood is most people don't seal it, or drill or cut into it without sealing it, and it rots.  This is my second year with my boat, and it's great, and I fish a LOT!   And 2 sheets made the front deck, and false floor, with some to spare, but I didn't deck the very front factory seat.  It's too narrow to stand up there often, so I didn't bother going that high.

361 is right,  Fl.  State certified Contractor and Certified Building Inspector