Taking it in turns relay style they had left from Hushinish, on Harris early Sunday afternoon to swim to Hirta, the main island in the St Kilda archipelago.
They had estimated it would take 40 to 50 hours to complete the 60 miles, which they were anxious to do before the bad weather forecast for later in the week.
But supporters following their progress on a satellite tracker thought the kayakers accompanying them were about to make it to their destination in less than half the predicted time. They expressed their delight on social media; "Just woke up and clicked on the tracker and I can't believe my eyes! They are nearly there!
But they were soon disappointed when another message was posted.
"Sorry folks but swim had to be called off at 5.30am sure to 5/6 for swells! Just wasn't safe for the kayakers getting in and out, they're all very disappointed but happy to have tried their best."
They were raising money for the Fishermen's Mission, Yorkhill Children's Charity and the Leanne Fund which provides treats for young people with Cystic Fibrosis in the Highlands and Islands.