That's cool. If you found multiple studs you can run a lateral brace (piece of wood horizontally) and use triangle shelf brackets (2 or 3 depending on how long the shelf is) it should comfortable hold more that 80 lbs (including the weight of the wood being used). It won't matter if it's drywall that is exposed to moisture because the weight would be held by the studs and the pressure will be distributed along the drywall by the lateral brace.
p.s. 80 lbs might be pushing it but will hold anything you decided to put on it.