Orkney Ferries officers have voted for industrial action in a pay dispute.
The Nautilus International union said its members opted to strike by a "massive majority", with a ballot showing 21 senior staff voting in favour and one against.
The union is willing to meet management for further talks, however.
Nautilus ferry organiser Micky Smyth said: "The ballot results are very clear and reflect the long-running frustration of our members about their pay and conditions.
"Independent research conducted in response to those concerns demonstrated that the salaries of our Orkney Ferries members are around 10% below those of other officers carrying out the same duties in comparable ferry companies."
The union is seeking a rise of 3.2% over the March RPI inflation rate, as well as seven days more holiday.
Smyth said management is offering 1.5%.
Orkney Ferries runs seven ro-paxes built in the 1980s and 1990s.
Orkney Islands Council told the BBC the industrial action "presents a considerable challenge" and that "there is the risk of service disruption".
A spokesperson added: "We remain committed to positive dialogue with the unions. But we have made clear we are unable to close the pay gap unless the council receives fair funding from the Scottish government for Orkney's internal ferries service, something which the council is continuing to work hard to achieve."
