The man who died at West Wittering beach on Saturday was a 32-year-old from Sutton in Surrey.
Sussex Police have confirmed the man went into the sea at the busy beauty spot just after midday to help a five-year-old girl who was being swept away by the tide.
He and a woman went to the aid of the child - the man passed her back to the woman, who managed to return her safely to the shore.
Sadly he was unable to make it back to shore himself and was recovered unconscious from the water.
“Despite efforts by members of the public and emergency services to resuscitate the man, he was pronounced dead at the scene,” said a Sussex Police spokesman.
“The family of the man have requested that their privacy is respected at this time. We hope to release his identity soon.”
The rescued girl, who was on the beach with her family, is from north-west London.
The Guildford woman was with a separate group from both the deceased and the child.
* Were you on West Wittering beach on Saturday? Please give the newsdesk a call on 01243 531313.