A man, woman and child have died and a seven-year-old boy is fighting for his life after getting into difficulty in the water.
Police Scotland said they were called to a report of concerns for people in the water near Pulpit Rock, Loch Lomond, south of Ardlui, on Saturday evening.
A 41-year-old man, a 29-year-old woman and a nine-year-old boy were pronounced dead at the scene.
The seven-year-old boy was rushed by ambulance to the Royal Hospital for Children in Glasgow, where he is currently in intensive care.
Please, please, be careful if swimming in one of the many beautiful Lochs and rivers across Scotland.
The past 48hrs have seen the deaths of 3 children (a further child is still missing), and 2 adults in water accidents.
Absolutely heartbreaking so please take care in water.
— DCC Will Kerr (@DCCWillKerr) July 25, 2021
A Police Scotland statement said it received the call at about 6.40pm on Saturday.
It added: "A multi-agency operation took place and sadly three people were pronounced dead at the scene.
"Formal identification has still to take place but the family of a 41-year-old man, 29-year-old woman and nine-year-old boy have been made aware."
A report into the incident will be sent to the procurator fiscal.
It brings the number of people who have died in Scotland after getting into difficulty in the water to five in just 24 hours.
An 11-year-old boy was pronounced dead at the scene after being found in the river at Alexander Hamilton Memorial Park in Stonehouse, South Lanarkshire, on Saturday afternoon.
A 16-year-old boy died in the water at Balloch Country Park, at the south end of Loch Lomond, on Friday.