Following on from Elizabeth's posting: The Convicts to Australia website
http://www.convictcentral.com/index.html is very interesting, if you think your ancestors or distant relatives went that way. If you are using a very good reference book, Never to Return, by Hampton Creer "The story of Manx prisoners transported to the penal colonies", which lists convicts and their ships and destination, it is possible then by use of the above website, to extract a little more information, including if you are lucky, physical descriptions.
Hampton's book, Never to Return, published by the Manx Heritage Foundation, PO Box 1986, Douglas, Isle of Man, ISBN No 0 952 4019 7 5