A better way to make a see-through (yet solid) object is use the transparency command (T), which can also be found as a checkbox in the color menu. Not only is it a useful way to quickly see into or through an object while you’re designing, it’s also a perfect way to create designs that look like glass or water.
Select the shape and after ticking the check box of transparency, you can able to see what’s inside the object.
Other method to see the transparency, select hole in shapes panel or press Ctrl+ h.
As a beginner you will often change the object from a solid (S) to a hole (H), to make it transparent. While this effectively makes the object look transparent, it can lead to accidental gaps in your design.