Southern California has been enjoying record-high water temps recently (yet somehow supremely-confused fullsuit-wearers still abound in pedestrian lineups), which means that if you do feel compelled to don any neoprene in the early morning or late afternoon, you want it to be light.

One of the better light wetsuits I’ve found this season actually isn’t neoprene at all. Patagonia’s new front-zip wetsuit top is made of 85 percent Yulex natural rubber and 15 percent synthetic rubber. What the hell is Yulex, you ask? Well, it’s what Patagonia calls a “Biorubber” sustainably harvested from the guayule plant—a desert shrub that grows in the southwestern US. Patagonia has been messing around with this stuff for years, raising the Yulex-to-synthetic ratio with each iteration, making these suits consistently more environmentally friendly than their petroleum-based counterparts.

But that’s not to say that making wetsuits from strange desert shrubs always seemed like a great idea. I was a guinea pig for an early version of a Yulex fullsuit, and it felt more or less like it was made of Brillo pads. It didn’t have the stretch of other suits and it was itchy enough that I thought I probably had a guayule allergy.

As it turns out, I’m not allergic to guayule plants (just coarse wetsuit linings) and the latest versions of the Yulex suits are as comfortable and stretchy as anything else you’re likely to find (you can find the top by clicking here). So while the water is hovering in the 70s, this light, flexible jacket is one of the better options you’ll find for when the air is cool, or if you’re just looking for a little something to keep the sun off your back.