Sea to Summit Flow 35L Dry Pack
$200, 35L/2,136 c.i., 2 lbs. 4 oz.
We reached the first, deep pool of water that we had to swim across in the narrow canyon called The Subway, in the backcountry of Utah’s Zion National Park. I tucked my expensive camera gear inside my new Sea to Summit Flow 35L Dry Pack, with my food and extra clothing—and hoped this pack would prove true to the company’s claim of being infallibly watertight. (I did put my camera gear inside another dry bag first, of course.) Then I dropped into the frigid pool—wearing a dry suit—and kicked across it, floating the Flow. And yes, it did keep its contents completely dry—thankfully. But more than just a glorified dry bag with shoulder straps, it proved itself to be a solid and comfortable pack for hiking all day, too.
I carried the Flow 35L with 15 to 20 pounds inside—including, at times, a full dry suit in a stuff sack—on a one-day hike and descent of the Subway in Zion, which took us just under seven hours car to car and involved three swims across pools, a lot of walking in water, and about six miles of hiking the trail above and below the Subway. The perforated foam shoulder straps and hipbelt were comfortable with that much weight, and drain water and ventilate well, and the hipbelt is removable to shed a few ounces of weight.
A top-loader with a roll-top closure for the main compartment, the Flow 35L is made with TPU-laminated, 420-denier nylon and is fully seam sealed. Water never penetrated the pack’s main compartment when I floated it across deep pools. You have to nearly fill the pack to create enough tension on the roll-top closure to ensure a watertight seal, but side compression straps help make a slightly undersize load watertight.
This pack is bulletproof—I slammed it into canyon walls and dropped it repeatedly onto rough sandstone, and it’s no worse for the wear. But the stretch mesh side pockets, big enough for a liter bottle, are its only vulnerable part. The upper compression strap on each side has two positions of attachment, to accommodate attaching objects of different sizes; I fit a fairly large tripod under the straps.
I didn’t quite fill the Flow 35L for the Subway, but 35 liters is a good size for technical canyon descents of a full day or even two days if you pack light, when you may be carrying a longer rope and more gear than we needed for the Subway. A white interior makes it easier to see contents. I like the big, top handle for lifting and lowering the pack through tight spaces even while wearing neoprene gloves.
Organization is basic, as expected in a dry pack (to minimize potential points of leakage). There’s a zippered, internal, stretch pocket for small items like keys and phone. A two-liter front pocket has a waterproof zipper with a rain hood; it keeps out rain and water if briefly immersed, but is not completely waterproof in a sustained immersion. There’s also an externally accessed, zippered pocket for a water bladder, so you can refill it without having to open the main compartment and potentially exposing its contents to water.
For canyon hikes when you’re in water, river trips when you want a dry pack that offers real support for 15+ pounds for side hikes, or any hikes in consistently wet environments, the Flow 35L Dry Pack is a durable choice.
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NOTE: I’ve been testing gear for Backpacker Magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See all of my reviews by clicking on the Gear Reviews category at left or in the main menu.