We immerse ourselves in it because our weight overcomes the so-called surface tension, a force that appears between the water molecules. Now, if it were only 5% more intense, we couldn't get into the pool.
However, there is a type of fluids that have very peculiar properties and that can allow us to walk on top of them. The liquids that we know, such as water or milk, always flow in the same way regardless of the pressure to which they are subjected. That is, its viscosity, the resistance to flow, does not change and is always the same. But there are other substances, such as ketchup, that do not follow this rule: they are called non-Newtonian fluids. In this case, their viscosity varies depending on the pressure applied to them. In the case of ketchup when it is inside the pot it is thick but if we shake it its viscosity decreases and it becomes more liquid, something necessary if we want to add it to our hamburger.
On the other hand, by mixing one part of water with two of cornmeal, the famous cornstarch, we will create a non-Newtonian fluid that has the peculiar name of oobleck and that behaves in a totally opposite way to ketchup: its viscosity increases when pressure is applied. . And there is the key to walking on top of it: moving quickly, thereby creating a quasi-solid column capable of supporting the weight of a person.
