Natural obstacles, with the exception of the liverpool and the water jump, tend to be used more in derby or speed classes. The course designer can still use them in other classes, though, so it's a good idea to become acquainted with them.
Sometimes natural obstacles can be placed between hedges or other natural settings. These can serve to make the jump slightly more spooky for some horses because they darken the area around the jump.
We'll start with the liverpool:
The water may be placed directly underneath the jump, or in front of/behind it. If it is placed in front or behind, there mustn't be a gap between the end of the tray and the vertical plane of the front of the jump. A liverpool cannot stick out more than 1 m in front of an oxer. Changing the placement of the liverpool serves basically to alter the ground line of the jump.
Moving on from the liverpool, we have the open water:
There is another version of the water jump that is more inviting and requires no extra judge on the ground, and it is therefore seen more often at levels where water jumps are introduced:
A jump that is slightly similar to the liverpool is the dry ditch:
A completely different type of obstacle is the table top bank:
The course designer can use flags to indicate where the horse should jump on and/or off the table top, or there may be jumps set against one or more of the sides. If there are no jumps used, only disobediences can incur faults at the table top. If only one jump or set of flags is used, the rider can decide which side to approach or leave the obstacle from to save time, depending on how it is set up.
The bank is a related obstacle:
The bank may also be used with a jump on top:
The bank can also be used to make a jump at ground level more difficult:
To learn about another natural obstacle, the grob or devil's dyke, see Natural Obstacles: The Grob.