The 15-year-old from India was with four other girls at Holdfast Marina at Glenelg on Sunday evening when they got into trouble.
Lifesavers were able to pull the others from the water but were unable to find the girl despite an extensive search.
Her body was found soon after the search resumed on Monday near the breakwater.
Two other girls aged 17 were taken to the Flinders Medical Centre on Sunday.
One remains in a critical condition while the other is stable.
Another 17-year-old is in the Royal Adelaide Hospital in a serious but stable condition and a 12-year-old is in the Women's and Children's Hospital in a stable condition.
City of Holdfast Mayor Stephen Patterson says the area is a treacherous spot and there have been previous drownings.
"There are signs near the actual breakwater itself alerting people to the fact there are strong currents," Mr Patterson told ABC radio on Monday.
Two boys drowned at a similar spot at Glenelg on New Year's Day in 2016.
The Indian High Commission said it was providing support to the group who were believed to be in Adelaide for the Pacific School Games.
"Very disturbing news from Glenelg beach in Australia," the Indian Department of Sports tweeted on Sunday night.
The Indian Australian Association of South Australia and Pacific School Games were contacted for comment.
