Arcan

Arcans were made mostly of liquid. A first-generation Arcan leisure crawler was described by Jack Harkness as a collector's item. Jack Harkness described the Arcans as "so boring", claiming that interrogating one could take up to a month for just one question. (TV: Cyberwoman)

History
In 2007, an Arcan leisure crawler was spotted flying above Cardiff, and was filmed by some people on their mobile phones, allowing Torchwood Three to identify it. The Arcans were politely persuaded to leave by the Torchwood team. (TV: Cyberwoman)