Recently I was on a ship and noticed the sea through the Hawser on the bow of the vessel. I had just been thinking about this exercise and thought it would fit and give me something different to work with. My first shot was taken with a Canon 5d Mark 3 set to Aperture Priority at f5.6 on a 70mm to 200mm lens from about 25 feet.
As you can see the depth of field allows us to see the deck machinery in perfect focus but the sea is out of focus. This would allow me to let the viewer know we are at sea without the sea being the subject. The second shot was taken from the same position with the same camera settings (however the shot is slightly different as the sea was rough and a tripod wouldn’t have been safe). The focus was set to infinity and the second shot taken.
This shot does the opposite to the first. it shows the sea as the subject showing colour and detail. But the out of focus foreground gives context without distracting from the subject. Allowing the viewer to see what you are intending to be the focus without any confusion. You can see the bollards but know the colour and detail of the sea is the focus.
Another variation that works well because of the rich colours and the fact I was outside the temple in Bejing. You could bring the focus on either the door or the statue making either subject stand out with out losing context.