The man, believed to be aged 74 and a regular at the pool, was taken to Dudley's Russells Hall Hospital but died shortly after.
Ambulance crews were called to the centre, in Wellington Road, at around 8.15am yesterday.
West Midlands Ambulance spokesman John Hawker said the man had been swimming at the time.
He said paramedics arrive to find the man was not breathing and resuscitation attempts were being carried out.
"Ambulance crews took over the emergency treatment and the man received advanced life support at the scene," he said.
"Resuscitation attempts continued in the ambulance en route to hospital who had been alerted to the man's serious condition.
"Unfortunately, despite the best efforts of everyone at the scene, ambulance crews and hospital staff, nothing could be done to save the man and he was confirmed dead shortly after arriving at hospital."
Dudley Council cabinet member Councillor Tracy Wood said said: "Staff did everything they could in responding to the incident and all of our thoughts are with the man's family at this sad time."
Staff at the leisure centre have refused to comment on the incident.