Two men have died and two more were rushed to hospital after a swimming accident at Llanberis, according to Wales Online.
Two more men, aged 25 and 27, were taken to hospital, but have been released.
The deceased 21-year-old was reported as missing at first.
A spokesman for RAF Valley said they were called out to the incident at around 8.30am on Sunday morning.
The group of four men got into difficulty in water at Ceunant Mawr Waterfall – a well-known spot in the local area that can be seen from the Snowdon Mountain railway. Otherwise known as Llanberis Falls, the spot is is situated a few hundred metres upriver from the town centre of Llanberis.