Neoprene certainly isn't waterproof (hence my plastic bag trick). If you want waterproof overshoes, it needs to be the ones that are made out of a rubbery material, rather thin, but very water resistant (if expensive).
My Altura nightvision gloves, despite having 'waterproof' embroidered on them, lasted about 25 minutes last night in the rain, then they got wet, but my fingers were nice and warm......