If you want a cool 3D sketch problem, Check out Google Sketch. Use a feet/Inches template, then zoom out to where you can enter your pond dimensions. With a bit of fiddling around you can draw the outline of the pond using your triangulation info, you will see the measurements as you draw. (Hint: Use SHIFT to log into a particular axis) With more fiddling, you can then extrude the pond volume. Even more fiddling and you can place structures, trees, etc. Before you know it you can loos a lot of time fiddling around.
Students have been using this tool locally and have come up some pretty amazing stuff, mostly architecture.
