It won’t even need to be raining to get your kid rushing to put on their shark rain coat. Turn your back and they will be outside seeking out the nearest puddle to jump into and slither up and down in. They will do so knowing that they will reach top speeds due to the low surface friction of their adopted ‘shark skins’ allowing them to zoom through water. This low viscosity is caused by shark skin consisting of millions of tiny denticles, ‘mini shark teeth’, that reduces water friction. Go on ask you kid, they will know all about it!