The Turtle was the first military submarine. It was built by American David Bushnell with the intention of sinking British warships during the American Revolutionary War.
A turtle is a type of robot which moves round on wheels on a flat surface. Its movements can be programmed in using a computer or it can programmed to perform pseudorandom movements. When it is low on energy it will return to its home for a power up. There have been recently ideas to try to use turtles to explain evolution. What happens is something like this: You have several turtles in a ring. They all have different functions. Some of them (the carnivores) will try to energy from the other turtles. Somehow the turtles reproduce other turtles (details not known, perhaps there are 'dead turles' which encounter a 'live' turtle).
Similarly, a virtual turtle was the basis of the turtle graphics system used by the Logo programming language.
There is an American folk-rock band called The Turtles, best known for the 1967 hit "Happy Together".