The tragedy happened at Yarrow Valley Country Park, off Birkacre Road, when the young man entered the lake shortly after 2pm yesterday (August 1).
He was seen struggling in the water and emergency services were called to the scene.
But despite the best efforts of those who tried to rescue him, the young man could not be saved.
His body was later recovered following a search of the lake.
Lancashire Police said there are no suspicious circumstances surrounding his death and his next of kin have been informed.
Police are asking for anyone who witnessed the incident to get in touch.
A police spokesman said: “We were called to the park after a report a man had entered the water and got into difficulties.
“Emergency services attended the scene and following a search of the lake, the body of a 26-year-man was recovered from the water.
“His next of kin have been informed and our thoughts are with his family.
“There are no suspicious circumstances surrounding the death and a file is being prepared for the coroner.
“We are appealing for witnesses or anyone who was in the area and might have information.”
Anyone with information can call 101, quoting log 728 of August 1, 2022.