The deceased M Dhanush of Old Washermenpet was a Class 9 student, said the Anna Square police.
The incident happened around 3 pm when Dhanush and four friends were swimming in the sea.
Dhanush and Logesh were sucked in by a giant wave and after their friends raised an alarm, Logesh was rescued by fire and rescue personnel.
However, Dhanush, who went missing, was found washed ashore a few minutes later. His body was sent for post-mortem examination. The Anna Square police have registered a case and further investigation is on.
This is the second incident of drowning reported at Marina beach in the past one week. Many residents are of the opinion that safety measures along the beach are lacking.