I haven't used coconut water before. What I do is add a can full of water to my curry to dilute the curry. This is in part to make it less calorie-dense and also to keep the sauce watery enough as the veggies simmer. Without water the sauce becomes very thick and starts to scorch. You can add a pretty decent amount of water to your curry without diluting the flavor.
You can also use lite coconut milk instead of regular.
Lastly, put a LOT of veggies in there. When you serve yourself, eat the veggies (or meat if you use that) and not the sauce part. The veggies will be sufficiently covered in curry to be delicious, but they won't be drowning in the curry sauce. My thai curry usually has a decent amount of the liquid curry part left over that I just throw away. I get plenty on my veggies and in my tofu and I don't really need the empty calories that pouring the sauce over white rice entails