Change the height of the walls with a value equal to the depth of the pool plus the height of its edge. Once done, select all the walls and choose the menu item Plan > Modify walls. Keep in mind to disable magnetism while you move the end points of the round walls, otherwise the magnetism behavior might prevent you from placing the point where you want. To get a bean shape, you'll probably have to make more than one modification, but after a while you should success.
To do that, draw a quadrilateral shape with points that will placed at key points of the pool, then modify the arc extent of each wall to get the round shape of the pool. You may draw a simple rectangular shape for a basic pool, but you can also draw a round shape, using round walls. Now you have to draw the walls in the underground level. Don't worry if there is no visual effect in the 3D view when you close the dialog box. You don't have to change the thickness and the height. Enter pool depth in Elevation text field, and change its name. Then select the Plan > Modify level menu item in order to make this new level become an underground level. Select the Plan > Add level menu item to add a new level to your home. To create a swimming pool, you will have to: This tips shows how to design a buried swimming pool using level, wall and room features available in Sweet Home 3D.
