A Police Scotland spokesperson said: “We were made aware that a man had gone overboard and caused a disturbance and made threats when he was rescued.
“A 23-year-old man has been arrested. The incident has since concluded and there is no threat to the wider public.”
Remaining sailings from Ardrossan were cancelled on Friday evening to allow crew to be debriefed and emergency equipment to be replenished
An extra service to the island was added at 19:50 on the MV Alfred from nearby Troon.
CalMac CEO Duncan Mackison said: “This was a fast-moving situation that was handled professionally by our crew, Ardrossan port staff and emergency services and I would like to extend my thanks and gratitude to them.”
The operator said affected passengers who had bookings would be contacted by customer services.
CalMac is the UK’s largest ferry operator, running 29 routes across 200 miles of Scotland’s west coast.
