Why Does Belly Flopping Into The Pool Hurt But Not Diving?

Have you ever tried belly-flopping into a swimming pool? If you have tried it before, chances are it probably hurts as you land in the water.

The swimming pool can feel a whole lot different if you jump into it flat with your arms and legs wide open. In fact, all of a sudden, the water seemed almost solid and hard. Why does it seem that way? Why does belly-flopping hurt more than diving into the pool? Let us find out more!

Dangerous diving

Landing in a water body may not be as harmless as many assume. In fact, there have been cases where Olympic divers injure themselves from entering the water at less optimal angles during repeated practices.

There are several factors that could result in any number of injuries due to jumping into a pool, with height being the main reason.

Your orientation is also a factor in how harmless or harmful leaping into water can be. There is a good reason why swan dives are the ideal pose when diving into a deep pool. Your entire body is orientated like a sharp arrow, which allows you to cut the surface tension of the water.

On the other hand, a belly flop often results in you landing belly or face first, increasing your risk of developing injuries.

So, why do belly flops hurt?

Water is a unique element. You can be in a swimming pool but do not sink. When you step into the swimming pool, the water feels welcoming, and the entry is effortless. However, it is a totally different feeling when you fall or jump into a pool. All of a sudden, the water “becomes” solid. And depending on the height you jump or fall from and your orientation upon entry, that solid feeling intensifies.

When you hit solid ground, your body immediately experiences the reactionary force. However, water is more dynamic and jumping into it displaces it. In return, the water exerts a force on your body. This force is proportional to the area of contact, your weight, and the height from which you jump or fall.

It is different when you walk into the swimming pool. The water gradually displaces. Hence, the reactionary force that is exerted on you is small. Hence, the higher you jump or fall from, the greater the velocity, resulting in a more powerful reactionary force from the water.

When you conduct a proper dive, your body decelerates at a much slower rate than if you were to belly-flop into the pool. This means that the reactionary force is smaller too. However, a belly flop means that your body completely hits the water in a shorter time.

The larger your surface area when you hit the surface of the swimming pool, the more water is displaced in a short amount of time, resulting in more reactionary force generated. This is why belly-flopping into a pool feels like falling on solid ground.

Surface tension

When you enter water, whether it is gradually stepping, diving, or belly-flopping into it, you will need to break the water surface. As you enter the pool, your body interacts with the surface tension of the pool.

The thing about surface tension is that the water molecules have stronger cohesive forces at the surface as compared to the rest of the water body. This is why you might find it harder to wade through water as compared to swimming under water.

Diving competitions often use aerators to generate bubbles which break the surface tension to protect and accommodate divers. All in all, the larger your surface area is when you come into contact with water, the more reactionary force the water generates.

When you swan dive into the pool, the tip of your fingers creates an entry point for the rest of your body. When you belly flop into the pool, the large surface tension has to be broken to allow your body to enter the pool. As a result, the water will momentarily feel hard as you break the surface tension.


All in all, the larger your body’s surface area is when coming into contact with water, the more resistance you will meet, resulting in a more significant and painful impact. Hence, in order to experience a painless dive, make your point of entry as tiny as you can, whether hands or feet first.

The world of physics is indeed an interesting landscape, especially when so many natural occurrences in our lives are a result of a physics theory. If this is something that you are interested in, then do not hesitate to reach out to Physics Tuition. Our classes not only ensure that you understand what you need for your physics exam, but they also grow your interest in the subject!