Coconut water is basically a natural isotonic beverage. It has about double the potassium as that of a sports drink, yet it contains less salt. It's low in carbs, low in sugars and 99% fat free. There are claims that it can help you lose weight, although I haven't seen results in myself. I think it's the most refreshing, tasty drink ever but I'm a little bias as I've grown up drinking coconut water straight from a young coconut. I haven't met anyone yet who can't stand the taste!
Coconut water hydrates your body, removes toxins, aids digestion and even has the same level of electrolytes as we have in our blood. It's been used to treat wounded soldiers in war and I believe that in some third world countries, it's been used as an IV (crazy, huh?)
In Australia, you can find coconut water in most grocery and health food stores, although most of the time it's in the non-chilled drinks aisle. There is a pretty nice variety to choose from, but I like to get mine from Coles. They stock Nudie's coconut water (chilled!) in 4 different flavours (nothing beats it "straight up", though). And it's not from concentrate. It's about $3 a bottle. Taste wise, it's the most natural as other brands add flavours and sugars to theirs, which defeats the purpose of drinking it for health benefits.
I like to have a bottle first thing in the morning, everyday (budget permitting, of course)! It's ultra refreshing after a work out. But I wouldn't know, I never exercise lol. It's good if you've been eating something spicy or salty, as it kind of neutralises your insides and you feel balanced... hard to explain. If you haven't tried coconut water yet, give it a try! It's both taste and health, bottled up.