Why swim trunks inflate and how to avoid it (2025)

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Swim trunks inflating, also known as “wedgie of the sea” or “ballooning,” is a common and annoying phenomenon that can occur while swimming. Not only can it be embarrassing, but it can also be difficult to deflate the swim trunks without drawing attention to the situation. In this article, we’ll explore why swim trunks inflate and provide tips on how to avoid it.

The short answer

Swim trunks inflate or “balloons” because water gets trapped inside the fabric. This is most common when jumping in the water or sitting in a hot tub or jacuzzi. To prevent this you can get tighter swim trunks that are not able to inflate as easily. If your swim trunks have already inflated then your best option is to help the air bubbles reach the surface. Just be aware of “farting” similarity when letting the bubbles out.

Our best tip: Avoid bubbles ever getting trapped by helping them out right when they are created. When jumping in the water, simply open up your waistband slightly and all air can safely escape right when you jump in.

Why swim trunks inflate

So, why do swim trunks inflate in the first place? The answer has to do with physics and the shape of the swim trunks.
The 3 main reasons that swim trunks inflate are:

Air gets trapped in the swim trunks when jumping in the water
Air gets trapped in the pockets of your swim trunks
Bubbles from a hot tub or similar find their way into your swim trunks and get trapped

1. Air gets trapped in the swim trunks when jumping in the water

When you jump into the water, the pressure of the water pushes against the swim trunks, forcing air into the fabric. The shape of the swim trunks also plays a role – swim trunks with a more spacious, baggy fit are more likely to inflate than those with a tighter fit. Cold water can cause the fabric of the swim trunks to contract, creating more space for air to enter. These factors can combine to cause swim trunks to inflate when jumping into the water.

2. Air gets trapped in the pockets of your swim trunks

Some swim trunks have pockets that can trap air when you are in the water. This can be especially true for swim trunks with large, deep pockets or those made of a lightweight, more porous fabric. If you have swim trunks with pockets, be sure to empty them out before jumping into the water to help prevent inflation.

3. Bubbles from a hot tub or similar find their way into your swim trunks and get trapped

Hot tubs and other bodies of water with a lot of bubbles, such as a pool with a fountain or waterfall, can also cause swim trunks to inflate. The bubbles can get trapped in the fabric of the swim trunks, causing them to inflate. To avoid this, be mindful of where you are swimming and try to avoid areas with a high concentration of bubbles.

The shape of the swim trunks also plays a role – swim trunks with a more spacious, baggy fit are more likely to inflate than those with a tighter fit.

There are a few other factors that can contribute to swim trunks inflating. Cold water can cause the fabric of the swim trunks to contract, creating more space for air to enter. Similarly, vigorous movement such as jumping or diving can also increase the likelihood of inflation.

Here’s a great example of what it looks like when your swim trunks have inflated in a hot tub:

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In conclusion

In conclusion, swim trunks inflate due to a combination of factors, including the pressure of the water, the shape of the swim trunks, and the temperature and movement of the water. To avoid inflated swim trunks, choose a pair with a tighter fit or a design that reduces inflation, and try holding onto the waistband or wearing a swimsuit with a drawstring while swimming. With these tips in mind, you can avoid the frustration and embarrassment of inflated swim trunks and enjoy your time in the water.

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