Robert Keenan said he watched in horror from the shore as his son Findlay, 7, and his young friend drifted nearly two miles out from the shallows in the dinghy.
The boys were playing at Thorntonloch beach, near Dunbar, on Saturday afternoon, while Findlay’s mum Sarah – and the four-year-old’s mum – were paddling beside them.
The latter started swimming, desperately trying to catch up to them after strong winds caught the rubbery dinghy – but they were moving too fast.
Mr Keenan, from Dunbar, said: “She ran to try to catch them but they were swept away quickly. She was a mile away from them. I saw this from shore and called the coastguard. I’m still shaking thinking about how quickly it all went wrong and what could have happened to my son and his friend.
"Findlay told me there were waves coming over the side and it was scary for him. I think his friend wasn’t so aware of the danger.
"Findlay only can do a doggy paddle for a short while and his friend can’t swim. The rubber dinghy is not strong so the chances of it flipping over were high.
"Letting your kids play in the shallows can lead to this. I remember watching it and felt absolutely helpless to save them. It was just horrendous.”
Dunbar Coastguard, RNLI Dunbar Lifeboats and Scottish Ambulance Service arrived at the scene to assist a vessel in recovering the mum and the boys and took them to Torness.
They were given the all clear by the ambulance service. The coastguard thanked the CNC Police and the nurse from Torness for their assistance.
Mr Keenan added: “I want to say the biggest thank you to everyone involved for saving my son and my friend’s son. There are not enough words of thanks for the people and response, including the protection vessel and coastguard. The police and nurses were all exceptional and totally above and beyond anything I’ve experienced.”
Posting on Facebook the Dunbar Coastguard issued a reminder to the public that inflatables are not for use in the sea.