Pics of the top secret propellor used on US nuclear submarines have been published on the Internet. 

A man browsing the Microsoft Virtual Earth service came across images of the Ohio-class ballistic missile submarine in dry dock – with the propellor clearly visible.
The US Navy is usually ultra-secretive about it's submarine propellors and they are usually seen covered with tarpaulins when the subs are above water.
The special design of the propellors allows the submarives to remain undetected while cruising.
The pictured submarine was in dry dock in a Washington state naval base.