The relief zipper installed on some men's drysuits isn't for use underwater. It's just for use on the surface, to save the hassle of partially removing the drys

The relief zipper installed on some men's drysuits isn't for use underwater. It's just for use on the surface, to save the hassle of partially removing the drysuit (can be difficult on small boats). But it's also a source of leaks so no one really uses them anymore.