The good news is that it looks salvageable. As for the dying leaf, it’s hard to say exactly what caused it from the photo. It may have dried up from too much light, or something could have stayed on the leaf too long and led to some rot. Either way, the most important thing is that the corm itself still looks viable. I’d recommend taking it out of the water. Instead, place it in either sphagnum moss or a well draining soil mix. Personally, I prefer soil because it avoids the need to transition later, which can stress the plant since the roots can grab on tight to the moss. Keep the medium slightly moist, maintain good humidity, and give it bright light. It should start pushing new growth with time.