Theo Treharne-Jones from South Wales was found dead in a pool at Holiday Village Kos on Saturday (15 June), the BBC reports.
A Tui spokesperson said: “We are aware of the tragic incident at the Holiday Village Kos, Greece, and our thoughts are with the family.
“Our team in-resort is currently supporting the family and we will continue to assist in whatever way we can.
“The safety and wellbeing of our customers and staff is our primary concern, and our dedicated resort team is working with the authorities and hoteliers.
“As the matter is currently still under investigation, it would be inappropriate to comment further at this time.”