 Ferry services link Orkney and Shetland to the rest of Scotland , the main routes being Scrabster harbour , Thurso to Stromness and Aberdeen to Lerwick , both operated by Serco NorthLink Ferries . Inter @-@ island ferry services are operated by Orkney Ferries and SIC Ferries , which are operated by the respective local authorities and Northlink also run a Lerwick to Kirkwall service . The archipelago is exposed to wind and tide , and there are numerous sites of wrecked ships . Lighthouses are sited as an aid to navigation at various locations . 
