Channel Four have a great series of documentaries on at the moment called 'Machines Time Forgot'. Last night the documentary charted the progress of a team of enthusiasts making a working turtle (a revolutionary submarine designed in 1776) based on original designs. They were successful in their attempt, which was a pleasure to watch especially since the hydro engineers at the Marine base where their testing tank was based, were initally very sceptical.
Article on The Turtle.