Shetland Islands Council operate an inter-island ferry service. All of them are available to foot passengers, and many allow cars. There is also an inter-island flight service.
A regular bus service operates around Shetland, and there are taxi companies.
Please be aware that the majority of the watch sites are remote and not well-served by public transport.
Visit https://www.shetland.org/visit/plan/getting-around to find out more.