The incident occurred at around 6:25 am when Phuong Tuan, 67, his wife and a 56-year-old man went swimming at the beach in Tinh Khe Commune.
All three were caught in strong currents and swept about 100 metres from shore, according to the My Khe Beach Management Team.
Pham Hoang An, deputy head of the team, said lifeguards immediately launched a rescue operation after receiving the alert.
High waves, rough seas and the distance from shore made it difficult for rescuers to reach the swimmers, but all three were brought safely ashore after about 15 minutes.
Quang Ngai's hydro-meteorological authorities forecast winds of level 4-5, gusting to level 6-7, and waves of 1-2.5 metres in waters off the province, including Ly Son, from Sunday night through Monday.
Beach officials advised residents and tourists to swim only in designated areas and heed safety warnings, with children and elderly swimmers accompanied by others.
People who see a swimmer in distress should alert lifeguards rather than attempt a rescue without appropriate skills. Swimmers swept offshore are advised to remain calm, stay afloat and signal for help.