Ivars Rubenis, 46, from Belmont Street was found unconscious in Marine Drive West at about 06:00 GMT on Saturday morning and was taken to hospital in Southampton.
He died on Sunday, and a post-mortem examination is due to take place later, Sussex Police said.
The cause of his injuries is still unexplained, a police spokesman said.
A man has died after being found with serious head injuries on the seafront in Bognor.