Foyle Search and Rescue were tasked by police at 1145 to reports of a male in the river.
We worked along with NIFRS, PSNI and NIAS in a controlled search of the area where the male was last seen.
A Coastguard helicopter from Prestwick in Scotland was also called to assist with the search.
FSR continued to search for a number hours, and returned later in the afternoon for a further search until we had to call it off due to fading light.
Our thoughts and prayers are with the family and friends of the young man in question; whom we believe is Jack Glenn in his early 20s, from the City.
We have been in contact with some of his immediate family and will be offering our full support to them during this distressing time.
We will be liaising with them on searches and any information we receive.
We have assured the family that we will be searching every day, at low tide if possible until Jack has been returned to his family.
If you or someone you know is in distress please contact Lifeline 24/7 FREEphone on 0808 808 8000 for confidential help and support.