DIY Question- waterproofing a truck box?

I built a custom sized storage box to fit into my truck last summer, and it was great. However, low and behold, the rains of winter came and with it, a little mold/mildew on the wood (and on the stuff inside the box because water of course got in). So I think I need to rebuild, figure out a way to do some sort of rubber seal to keep water out, but also make sure that the wood itself doesn't just keep getting saturated.

What kind of wood would be best for something like this? Best way to weatherproof? (Epoxy, varnish etc?)

Thanks DIY!!

Submitted March 31, 2016 at 05:54AM by jumpin_jumpin http://ift.tt/1M1CfTu