Jessica and Nelly Korda in 2015 at Coquina Beach in Bradenton Beach, Florida.

The Korda family has ties to Florida, and it’s plausible that they visited or spent time at Coquina Beach.
Both Jessica and Nelly Korda have a strong athletic background, with Jessica already playing professionally in 2015. It’s possible they were engaging in physical training or leisure activities at the beach.
While it’s impossible to definitively confirm that the photo is of Jessica and Nelly Korda at Coquina Beach in 2013 without more information, the visual details and contextual clues suggest it’s a possibility. The setting, the subjects’ ages, and their athletic appearance align with what we know about the Korda sisters and their background.
It’s important to remember that without further verification, this remains an inference based on the available information.