Gulf World management says Angel, a bottlenose dolphin, has died.

Management says Angel passed away Sunday morning after being seen swimming normally. The exact cause of death is unknown at this time, but Angel was being treated for a long term fungal infection that has up to a 98 percent fatality rate in dolphins.

They say despite this infection, Angel had not shown visible signs of illness and was behaving normally. They say a necropsy was conducted immediately and the findings are still being investigated.