Here is the size chart for choosing the Watery Hedgehog wetsuit for children. The measurements are taken with the suit lying flat and without stretch. The wetsuit will stretch both with use and in the water, adapting to the body during swimming. Therefore, choose the size based on the measurements you are closest to.
If you happen to fall between two sizes, choose the one where you match the most measurements. In general, the most important measurements are chest and height (ankle to shoulder).
A wetsuit should not fit too loosely, so if there are many air pockets or “bags” forming around the suit, it is too big for you.