It's pretty hard to overdose on water unless you're in some state like extreme dehydration where water consumption needs to be overseen by a doctor. Unless you're talking about drowning, then you're just being silly. As a healthy adult, drinking too much water until the point that you're injured is hard to do. You likely need a mental disorder to ignore simple signals like "my stomach is very full right now". Whereas OTC medications can be very easy to overdose. If you don't read the instructions and regularly take more than recommended, you can injure your liver or other organs. Pills are not very big so a handful of them can easily be in the LD50 area.

Oxygen toxicity is not a risk for most people. You either are a scuba diver regularly working at depths beyond what most do or are taking supplemental oxygen while under the care of a doctor. You are not at risk of oxygen toxicity reaching into your bathroom medicine cabinet.