I attempted to make coconut yogurt last night and succeeded in making a layer of thin yogurt over a layer of coconut water. Hm. It's got the tangy taste and smell of yogurt but it's quite watery. I'm drinking this batch and will try again this weekend.
I think I went wrong by watering down the coconut milk. The can I have - A Taste of Thai Organic Coconut Milk - is as thick as sour cream, so I was afraid to use it full strength. I mixed it with a can of Goya Coconut Milk (which I'll never buy again - it's so watery and tastes adulterated with chemicals and added fats and is very dilute), and added some water. I heated it per usual, cooled it down, and mixed with a packet of Yogourmet starter.
The end product separates into a creamy liquid top layer, a watery layer underneath, and a thin layer of sediment at the bottom even after I've stirred it together.
It is, however, delicious. :)
Will try again and post results!