There should be 4 types of plywood at your Lowe's.
CDX---Construction plywood with alot of voids and "football" fillers. The C is a grade for 1 side of the plywood. The D is a grade for the other side. Should be available in 3/8, 3 ply 15/32, 4 ply 15/32, 19/32, and 23/32.
BC Sanded---A little better grade. The B side will most likely be smooth because it is sanded with very minor imperfections if any. The C side will have a few imperfections. Should be available in 11/32, 15/32, 19/32, and 23/32.
AC---The A side will be perfect and sanded. The C side will have very few and small imperfections and it will be sanded as well. Should be available in 15/32 and 23/32.
Pressure Treated---As the name says, its pressure treated chemicals to make it resistant to moisture and insects. (stay away from this as it will react with the aluminum in your boat)
At the Lowe's I work at, the CDX, BC, and AC were all made with an "exterior glue". They all say for interior or weather protected use.
In my build, I used the 15/32 BC Sanded and coated it with several coats of the Helsman Spar Urethane.