Do you believe ads that claim oxygenated water cures tiredness, improves memory, prevents diseases, treats lung disease, helps you to exercise longer and makes you a better athlete? These and all of their other claims are not supported by scientific evidence:
• Hydrates cells better than plain water (no)
• Transports extra nutrients to your cells (no)
• Activates your immune system (no)
• Slows aging (no)
• Promotes weight loss by burning fat (no)
• Detoxifies and eliminates waste (no better than ordinary water)

If you were a fish, you could use your gills to extract oxygen from water, but since humans have no gills, you need to get your oxygen through your lungs. Lungs are the only organ humans have to provide adequate oxygen to the bloodstream. Water is not broken down into hydrogen and oxygen in your digestive tract; it is absorbed, used and excreted as water. Since you have no intestinal mechanism for moving extra oxygen from water into your bloodstream, oxygenated water cannot possibly help you with exercise or anything else.

All water has a little oxygen dissolved in it and pumping oxygen into water under pressure can add some extra oxygen, but as soon as you open the bottle, the reduced pressure allows oxygen to rapidly pass from the water into the air. What little extra oxygen may be left in the water will not be absorbed from your stomach and intestines because they do not have the oxygen-transport membranes that your lungs have. One breath of ordinary fresh air contains more oxygen than four cups of hyper-oxygenated water, so one deep breath will bring more oxygen into your lungs than oxygenated water would deliver to your stomach, even if your body could use it (JAMA, Nov 12, 2003;290(18):2408-9).

How Athletes and Exercisers Use Oxygen
When you exercise as hard as you can, you gasp for breath because you are not meeting your needs for oxygen. Lack of oxygen prevents you from breaking down lactic acid so it accumulates in your muscles and blood, your muscles burn from the acidity caused by lactic acid buildup and you become short of breath from trying to bring more oxygen in through your lungs.

Breathing extra oxygen during all-out exercise does help you to exercise longer and harder (J Physiol, Jan 1, 2008;586(Pt 1):25–34), but drinking oxygenated water does not deliver extra oxygen. Researchers analyzed the effects of drinking oxygenated water daily for two weeks on lung function and clearance of lactic acid from the bloodstream during exhausting exercise. During both exercise and rest, there was no difference between people who drank oxygenated water and those who drank ordinary water as a placebo (Br J Sports Med, Sep 2006;40(9):740–741). Taking oxygenated water did not increase VO2max or exercise performance.

More Evidence That Oxygenated Water Does Not Improve Athletic Performance
Another study showed that drinking 500cc of oxygenated water did not raise resting, submaximal or maximal oxygen uptake (VO2max), improve blood circulation, lower blood lactate at rest or during exercise, or help athletes recover faster from exercise (Br J Sports Med, October 2006;40(9):740-1). One study showing that oxygenated water increased lactic acid clearance to improve exercise recovery (J Int Soc of Sports Nutr, March 29, 2017;14(9)) was paid for by a company that sells oxygenated water, and even that study showed no improvement in performance.

My Recommendations
Whenever you see an advertisement for a product that is supposed to give you special health benefits, be skeptical. In the U.S., the Food and Drug Administration (FDA) is authorized to regulate health claims on the labels of foods, bottled water and supplements, but when manufacturers want to make unproven claims, all they need to do is add a disclaimer that says, "the FDA has not evaluated this claim." Claims made in ads for these products, particularly on the internet, receive even less scrutiny. There is no government agency that actively protects you from fraud or nonsense. I recommend that you save your money.