I constructed a deck storage box (24 x 48) about 4 years
ago and used poly glue for the M/T lid and for the butt joints
on the box. I stained it with semi-transparent (Behr)
stain.

No problems so far - joints still tight (allowing for the
P/T wood shrinkage factor).

It is not adjacent to the pool, so not soaked daily. I cover it woth a
tarp during the snowy months, but not during the rainy spring/
summer/fall.

Lou