Now that it's snowing outside here in Calgary, of course, is the perfect time to whip out the Swimming Templates! (this, by the way, is template id#35273)
But to make your own reflections, here is a little tutorial:
First, start with an image (any image, picture, embellishment, etc) and make it the size and angle of rotation that you want it at. Copy it, and then paste second copy of the exact image/size/angle.
Next, go to the "layout" tab in your toolbox and flip your image horizontally. Place the upside-down image where it would go if it were actually reflecting your first image.
And that's all there is to it! But check out the possibilities: