Up to his belly button

Years ago I came up with some catch phrases to explain distances, size and amounts to my children.  When we are shopping they are to stay in high-five range (close enough to give me a high-five).  You need to try as many bites of a new food as you are old and so forth. When my two youngest boys asked if they could take a bubble bath I agreed, but reminded them that the water should be no higher than Peter's belly button, since he is the younger and smaller of the two. My back was turned during this conversation so I missed John measuring to see where Peter's belly button was.  I am grateful Melissa saw and quickly added "When he is sitting down!" Emma chimed in "Sitting on his bottom!"  We wanted no misunderstandings or floods in the bathroom. You can never be too careful, especially with those two.