We've tested Levi's Shrink-to-Fit 501XX (STF) and the regular 501 jeans to compare them with regular swimwear like soft, knee-length shorts. For this test we combined them with matching swim shirts.

Dry Test

The STF jeans felt a bit baggy and stiff when new. This soon changed after our tests. We used a belt to keep them in place, until they shrank in size.

We've climbed across the rocks on the beach and hiked through the hot tropical forest of northern Thailand. In both places the jeans were quite comfortable.

The fabric is robust enough to protect from minor scrapes when you scramble across a wild coastline to get to an exclusive beach.

The button fly can't get jammed by mud or sand like a zip. The buttons stay put whilst a zip my wear out and slide down.

Swim Test

We've tested our jeans in the sea, and the wild canyons and lakes of northern Thailand which was great fun. We often jumped into the water and climbed back onto the rocks to see what it is like to move about in wet jeans.

When wet, the denim fabric initially got a bit stiffer as it swelled with soaked up water. But it was still comfy to jump about on land and in the water. After several swims the fabric began to soften a bit.

The Levi's 501 jeans are great for swimming. They are tight enough for easy swimming, but loose enough to move freely. They feel good in the water and look cool with tight fitting T-shirts and large hoodies.

Comparison

Shorts and Swim Shirt are great for swimming pools, but not so good around open water. Our team felt a bit unsure wearing just swimwear while hopping around the rocks. Although it was easier to swim in and didn't soak up as much water, it left a lot of bare skin exposed to rocks and sunburn.

Jeans and Pullover provide better protection for adventure swimming, but felt somewhat heavier out of the water, and slowed us down when swimming. However, we think this outfit is far better for splashing about and messing around in boats. Another advantage is that you keep cool on hot days and don't need to bring extra swimwear. Just jump in as you are.

Summary

We prefer the shrink-to-fit (STF) versions as they fit better the more you soak them. The trick is to keep them on while they dry. You better do that in a warm climate.

Jeans are Better than Board Shorts

Jeans don't fall off when diving into a pool like some boardshorts, which are the worst clothing to swim in. When wading in waves on the beach boardshorts billow up between your legs and chafe with the sea, sand and saltwater. Jeans just fit well.
~ Joey, NSW, Australia 

Skater Kit

I love swimming in jeans, also in my skater kit, like hoodies and such, which is so awesome. People look at me, maybe thinking wet jeans are hot.
~ Cody, Oregon, USA 

Cool Cotton

Cotton jeans can get cold quickly once you come out of the water. Unless you intend to hop right back in, change into dry clothes between swims.

My sea swimming team occasionally goes on excursions to nice beaches. We take a few jeans, hoodoes and T-shirts if we plan to take several breaks.

In between swims we change into dry clothes. It can be tricky to put on tight wet jeans, so we go back into the water in the dry clothes.

~ Andrew, Brighton, England