Cal Mac has stopped taking ferry bookings for a week due to the RMT crews’ strike.
Western Isles ferries are expected to be tied up in port throughout Friday as crews down tools.
And passengers are being advised to expect further disruption the following day, due to the huge backlog in stranded traffic.
Crews are striking over fears about job losses, cuts to income and pensions in the face of transferring state-owned Cal Mac’s lifeline routes to a private operator.
The industrial action has hit crowds of islanders attempting to head away for music festival T in the Park.
Tourists and islanders planning island travel are also forced to make alternative arrangements.
Bed and breakfasts and hotels face cancellations as the uncertainty over Hebridean bookings mean some visitors opt to go elsewhere.
Cal Mac said it has suspended advance reservations because the RMT strike “is likely to cause severe disruption” and that it had been ruled necessary to stop bookings.
“Should the situation change and industrial action is averted, we will open the booking system back up to our customers,” a spokesman said.
“Cal Mac would like to apologise for the impact this disruption may have to our customers.”
An earlier strike caused chaos with no Western Isles ferries sailing at all.
Tourists and islanders were stranded, businesses lost money, and the subsequent backlog of ferry traffic created more travel problems the following day.