I mentioned earlier the risk of wind and current pushing the kayak in a direction - unperceived by the paddler - other than the intended direction. I mentioned that we used GPS to track our bearing to a point, and if the bearing changed we were moving side ways in addition to forward. There is a way to track this without GPS, and it is only difficult to explain, not difficult to accomplish.
So if you are paddling your kayak in a straight line towards a point, your bow and that point will line up. So lets say you are paddling your kayak to the tip of an island. You have a clear point you are paddling too. But lets say behind that island there is a mountain. and the summit - or in the case of the photo where the mountain meets the sea - there will be another point. So now you have three points you are keeping track of 1- your bow. 2 - the tip of the island, and 3- where the mountain touches the sea. All three are lined up. 1,2,3. But as you keep paddling, you realize point 3 - where the mountain meets the sea - starts to drift to the right, while your bow is still pointed at the tip of the island, this means your kayak is drifting to the right. Likewise if the mountain moves left while your bow is still pointed at the island, you are drifting left.
You can visualize this right now sitting in front of your computer. Close one eye. stick your right hand out with your arm straight and your index finger pointed up. Put your left hand out halfway between your right index finger and your open eye, also with the index finger pointed up. The two fingers should line up. Now move your head to the left and the finger furthest from your nose will also move to the left.
This is an amazingly useful tool. You can use any two points of land. A point of land and a summit. A buoy and a point of land. You are only limited to using things that wont move. It is an excellent way to judge your position on a crossing as long as you can find two points that line up.
image 1 - three points lined up.
Image 2 - drifting right.