A SNH diver on a previous survey around St Kilda
What lies beneath the waters around an island forming Scotland's most remote national nature reserve is to be surveyed for the first time.
Divers will investigate kelp seaweed forests and sea caves used by grey seals at North Rona, 47 miles north of the Butt of Lewis in the Western Isles.
Scottish Natural Heritage (SNH), which owns the island, has chartered a survey ship for the work.
North Rona, now uninhabited, was at one time was used for grazing sheep.
The SNH team, led by Dylan Todd, will carry out the work in two stages, starting next week.
An initial eight day sweep of the sea will be made using the Orkney-based Ocean Explorer.
Mr Todd said: "We'll be gathering a huge amount of information on the rich and diverse marine life surrounding North Rona in order to develop a management plan to help protect the area.
"We expect to find kelp forests extending as deep as 35m and areas of open rock supporting rich marine communities of sponges, anemones, soft corals and ascidians."
Information gathered from exploration of sea caves will be passed to the Sea Mammal Research Unit, in St Andrews.
Rock samples will also be gathered for the British Geological Survey to conduct geological analysis.