Steven Doorey-Williams, who owns Bayside Cafe at Dumpton Gap near Broadstairs, was working on Tuesday when he heard screams. He reportedly saw a boy and girl struggling in the water and used a nearby life ring to help them back to shore.
After returning the first two children to the beach, Mr Doorey-Williams noticed a third child in distress and went back into the water to assist them.
His actions have been described as "absolute hero behaviour" by people in the area. The RNLI also praised his efforts, but its south east water safety lead, Guy Addington, cautioned that entering the water to help someone can put additional lives at risk.
Mr Addington advised that if someone is seen in trouble in the water, the public should always phone 999 or 112 for the coastguard, encourage the person to float on their back, and throw them something to help them stay afloat.