Harborview spokeswoman Leila Gray says one man died Friday. The other died shortly after he was brought to the emergency room.
Seattle Fire Department spokesman Kyle Moore says the two were unconscious and unresponsive when divers found them Thursday night.
They were not immediately identified.
One had reportedly been underwater for 30 minutes and the other for 45 minutes.
A total of four men had decided to go for a swim about 9:30 p.m. Thursday but only two made it back to shore.
Witnesses saw the other two men struggling. One of the witnesses went in after the men, but couldn't find them. Other witnesses stayed on shore and called 911, according to Kyle Moore with the Seattle Fire Department.