Michael McLaughlin, 38, a New York filmmaker and editor, was snorkeling by himself near Tulum, Mexico, Sunday when he apparently ran into trouble, the Chicago Sun-Times reported Wednesday.
A bystander on the beach noticed that something was wrong and alerted Schakowsky, Creamer and McLaughlin's wife, Lauren, who sped to the scene in kayaks.
By the time, McLaughlin was brought ashore, it was too late, the Sun-Times said.
The incident occurred while Schakowsky, Creamer, their children and grandchildren were gathered Sunday for a belated celebration of Schakowsky's 65th birthday.
Lauren McLaughlin is the daughter of Creamer and his first wife, Day Piercy.
Schakowsky lost her daughter-in-law Fiona to cancer in July 2005. Fiona was married to Schakowsky's son, Ian.