A transit line is a simple way of paddling more effectively. It will let you save time and effort.
A transit line is created by lining up two fixed objects, creating an imaginery line across the water.
The paddler in the photo above is using a post and the mountain in the background as a transit line. If, from his perspective, the mountain is moving to either side of the post, he knows he is veering off the transit line. The paddler must keep the post fixed at the same spot on the mountain in order to paddle straight.
This simple technique is useful when wind and/or currents are pushing your kayak off your desired course.