Being a landscape painter from way back, I knew it was only a matter of time before I gave this program a try. After only a few hours I knew I was hooked, and although I found it easy to generate land it was a little more difficult to achieve a water scene. 

I wrote this tutorial for the benefit of those that want to create water scenes and need a better understanding of the theory behind achieving this.

The first thing you will have to do is generate or load a pre-existing terrain. If you have not already generated a sky, you will want to do this next. After these two steps are completed you can choose your camera and target position 

The render control menu will allow you to see any changes you might make, or to display your final rendering before saving it to a bmp file. Sliding the detail slider to the right will give you the best quality although it will taker longer to render. Obviously the finest detail, is the best option to see exactly what your finished scene will look like.

The lowest quality because of it's fast rendering is useful for checking out minor changes such as sun position, camera angle changes etc.

After you have rendered a landscape suitable for your needs, you can add water by clicking on the tool bar that appears on the left hand side of Terragen. The water menu is represented by the following icon.

Once the water menu appears, you are ready to start entering your water data. 

In order to get water in your generated terrain, the most important factor you will have to set is the water level. This number will continually change with each terrain you generate, and will also be dependent by the camera and target position of each scene. Although the program default number for the water level is set very high, you will in all probability have to set this number quite low to achieve water.
 

The pictures below are meant as guides to help you understand the different steps you will have to go through in order to add water to your scene. Remember that these are only meant as examples and that your numbers will vary depending on your own terrain , camera and target positions.
 

The easiest way to find your water lever is to start with a very small number such as -1, and from there continue to go up in increments of 5 or 10. Example: -10, -20 etc.

Sometimes you will be lucky and -1 will give you water right away, if this doesn't happen, continue to go up until you get a black hole such as picture number 2

When you find the number for the black hole, continue to go up until you get the number that will give you complete land again. The area between these two numbers will be the range for your water level.

The horizon is where sky would meet land if there were not mountains etc obstructing your view.

#1 water lever set at -20 This number would represent the highest and uppermost limit that would still give you all land, before becoming a black hole.	#2 The black hole Water level set to -10  This would be the lowest number set for your water. Since there is no water showing, you will have to go up a number or two for it to appear.	#3Now that you have an high and low mark, you can play within those ranges to give you different combinations of land and water. The water lever for this picture was set to -15  Middle of the road between the highest and lowest numbers.
#4 Since you know that -15 in example number 3 resulted in both water and land below the horizon, you can work your way down until you obtain all water below the horizon. In this case -14 or -13 etc	# 5 Now working the other way from the middle of the road, work your way up to give you the smallest amount of water possible. In this case -16 It's easy as that. Once you understand the fundamentals behind this theory , you can achieve water in ever scene if you wish.	# 6 Once you master water, you will have to experiment with the lighting menus to give your scenes different looks. Remember you are only limited by your imagination and creativity. Have fun :)