Barry Davis Ryan disappeared along with his father, also named Barry, and his girlfriend, Niamh O'Connor, in Baltimore, County Cork.
Mr Ryan Sr, 51, and Ms O'Connor both drowned and their bodies were found on the day of the incident.
It is understood all three were part of a group walking close to the harbour when one of them fell into the sea.
Two others then went into the water to try to rescue the first person, but all three got into difficulties.
The body found on Friday will be taken to Cork University Hospital where a post-mortem examination will be carried out.
Official confirmation on the identity of the body is expected over the coming hours.
A body has been recovered in the search for a man who went missing off the Irish coast on 30 June.