The 36-year-old woman was pulled from the lake at Walsall Arboretum on Wednesday morning by fire service rescue swimmers before being taken to Queen Elizabeth Hospital in Birmingham.
However, Walsall Police later confirmed that the woman had died, adding that her death was not suspicious and her family had been made aware.
A spokesman for Walsall Police said: "We're sad to say that a 36-year-old woman has died after she was rescued from a lake in Walsall Arboretum this morning.
"Her death is not suspicious & her family are aware.
"Thank you to those who tried to save her.
"Remember that the Samaritans are there if you need someone to listen to you."
Emergency services were called shortly after 8.30am on Wednesday after receiving reports of a woman in the water.
Fire crews from Woodgate Valley and Walsall, as well as those from Willenhall with specialist equipment and the technical rescue team, were among those who responded.
A West Midlands Fire Service spokesman said: "Working with West Midlands police and ambulance services, and with the aid of an ambulance service drone, two of our rescue swimmers retrieved her from the water.
"She was taken to hospital by ambulance."
Witnesses reported seeing crews by the bandstand at the Arboretum.
A West Midlands Ambulance Service's specialist Hazardous Area Response Team was sent to the scene along with an ambulance, two paramedic officers and a critical care car.
A spokeswoman for the ambulance service said: "Upon arrival, we found one patient who was a woman in a critical condition, she received treatment on scene and was conveyed to Queen Elizabeth Hospital Birmingham for further treatment.”
“We were called at 08.32 to reports of an incident in the water at Walsall Arboretum, Walsall. One ambulance, two paramedic officers, two Critical Care Cars from Midlands Air Ambulance and the Hazardous Area Response Team (HART) attended the scene.
* If you have been affected by this article, you can call the Samaritans on 116123 or visit Samaritans.org.