Police were called to a popular snorkelling spot near Owaka Heads at Hinahina, south of Kaka Point, about noon yesterday and a search was initiated.
By 1.40pm, the man was found but could not be revived.
"Sadly, he was not able to be revived and was pronounced deceased at the scene," police said in a statement.
The death will be referred to the coroner.
In 2018, two South Otago friends died while diving for paua further south in the Catlins, in Purakaunui Bay.
Stuff reported Senior Constable Murray Hewitson, of Owaka, as saying the diver was a 23-year-old man, who had connections to the area “but doesn’t live here’’.
He said the man was out freediving with a family member, when he “seemed to have come into strife”, Stuff reported.