- ARC Ataa Alresalah
- 90.3 square metre(s)
- Saudi Arabia (Jeddah)
The largest flag unfurled underwater measures 90.3 m² (971 ft² 141.27 in²) and was achieved by ARC Ataa Alresalah (Saudi Arabia) in Jeddah, Saudi Arabia, on 29 September 2017.
The flag unfurled underwater was the flag of Saudi Arabia. The attempt happened during Saudi National Day.