I need ideas for the top of an outdoor storage box
So far I have a stuccoed block wall with a concrete base that runs about 20' x 3.5'. I'd like to put a top on it that can open for storage, but will be use as seats /lounge chairs out by the pool. The lids should be waterproof for when it rains. Not to heavy so it can lift up- (probably in about 6' sections), but strong enough to support the weight of people on it. It also can't get too hot in the arizona sun (I plan on buying cushions to cover them, but the edges worry me). I am looking at some of the soft lid support hinges so it won't catch fingers on the way down.
I'm afraid a hardwood would be too heavy, a plywood, not waterproof, a metal too hot, and sharp on ends.