Rivers and harbors.

You can create the illusion of the depth of the water with various shades of paint. I used a very simple approach with high gloss paint and several coats of urethane sealer. I had a lot of area to cover. The wet look of the water is obvious.

Fred - I plan to make my fascia first and then run the river or lake right up to the fascia.  I hope to make it look like you have just sliced through the earth there.  Then the river will continue in your imagination beyond the fascia.  I haven't done it yet so I do not have a picture.

Art

I have done something similar to what Art said above.  The water goes to the edge of the layout where the fascia piece is which is painted a flat black.  I use shower door glass as water and paint the Masonite the glass sits on a dark algae-like green.  Some folks paint the bottom of the glass....

Alan

Take a slow tour through the Your Layout Vignettes thread on this forum.  There are some great harbor and river scenes there.  Leavingtracks has an awesome urban harbor that is a great example of modeling something like the river in Chicago or the harborfront in any big east coast city, with all the attention to detial needed to get the complexity of a big inner metro core.  Others including my layout have quieter country river of lake/water scenes.  

There is no right or wrong way to do these - but maybe looking at a lot of other layouts will give you ideas on what is right for your layout.

Very nicely detailed Mark.....  The trees are awesome....

My little lake.

The trees are jute rope that is unraveled, painted black, and covered in flake foliage. 

The West End of the Lionel Man Cave Layout • Trainroom Gary

This is a photo of a PENNSYLVANIA Steel Girder Bridge over Pine Creek. D T & I is on the main line. Great fishing for all.

Click to enlarge photo

This is a 24" wide section of wet lands at the side of the layout, looking at it from a dirt road.

This river is still under construction, have some bank work to do before adding the glossy stuff-