Functional bikes. Not Porn not Anti

Are any of the rando bags really that waterproof though... they all have stitched seams and huge top opening... I suppose you could go all out and have a floating welded roll-top inner, but that'd add weight, cost and compromise ease of access.

With any bike-luggage solution you should always be stashing stuff in dry bags if you don't want it getting wet, whatever the manufacturer claims.