I searched "percent" and didn't see this joke, so hopefully not a repost.
An older guy was a heavy drinker (only 96 percent of course) and never even touched water. His kids always told him to hydrate more and cut back on the alcohol. He eventually ends up in the hospital and the diagnoses is water in the lungs. He turns to his kids and says: "See! The 4 percent is gonna kill me!"