I've got ones from the Muck Boot Company and they are 100% waterproof including the neoprene bit. Not sure about other makes.
These are the ones I have
https://fhwbrands.com/products/mens-muck-boots-chore-classic-tall-xpress-cool-wellingtons-bark
They are quite pricey but I use mine loads when walking the dog so see them as a good investment (especially considering how crap the weather has been)