Nothing yet. Sorry this ain't the best riddle in the world. I just banged it out in a minute for something to do. I noticed a slight error that might lead people astray so here's a rewrite with minor alteration.
A full moon sits now o’head,
Waves and rocks at hand,
Eighteen score, no less, no more,
The cold and careless band.
Plastic, tree, and cloth ‘tis me,
I carry what you covet;
So long as rain from deck abstain,
My purpose lies above it.