Well, at least be cautiously optimistic. If you've heard of "mondo grass," this stuff is another non-aquatic that's often sold as an aquatic, and it can actually survive and even put out new growth under water for months. At some point, however, it supposedly starts rotting away. Never tried it myself...
Whether or not you manage to keep it alive for the long-term, it's a beautiful plant for now. If you do start noticing degradation in the condition of the plant, you should remove it immediately. Good luck!
-Naomi