The Sea to Summit Hydraulic measures 13-inches wide x 8-inches deep x 28-inches tall. This 35-liter pack is made out of 600D TPU laminated nylon and sports a removable backpack harness with padded shoulder straps and a nylon waist belt. It also features four welded nylon lash patches for easy attachment to your craft of choice.
This model features a comfortable removable backpack harness.
While overall, this product does well, this metric is where it fails to shine. Our gear stayed dry with casual use and when exposed to splashes. Upon submerging it, a fair amount of bubbles escaped, but only a few drops of water entered the main compartment. Unfortunately, when put to the rigorous task of being dragged behind a paddle board through a lake, it on-boarded a significant amount of water, and our testing towel was soaked.
Some large bubbles escaped during our submersion testing.
This product may serve well for casual river days or to store gear that you would rather stay dry, but it won't be a total deal breaker if some moisture gets in. If you're worried about your raft getting flipped and your bag getting dragged through the white water, we tested several other options that offer significantly better protection.
Our testing towel ended up pretty soggy after submersion.
Ease of Use
The Hydraulic has a long and narrow design with a single opening at the top. This means packing from the bottom up and stacking your contents. It's also difficult to reach to the bottom of the pack.
This model is quite comfortable to carry. A handle at the top of the backpack makes a nice handhold when the pack is off your shoulders. The backpack straps are also well-padded and adjustable. Unfortunately, the 35-liter model has a webbing waist belt that is a bit painful on your hips with heavy loads.
This handle made it really easy to pick up the bag and we found this feature surprisingly useful.
Padded Waist Belt
This model also comes in 65-liter, 90-liter, and 120-liter sizes. Each of these larger models features a padded adjustable waist belt more like that of a typical backpacking pack.
The Hydraulic scores well in this metric due to its comfortable backpack frame that is quick and easy to remove and reattach. Fully-adjustable shoulder straps make for a more custom fit, and anodized aluminum buckles provide durability. While these buckles are convenient to slip on and off, they are also prone to popping off mid-use. This doesn't greatly compromise the functionality of the product, but it is a bit annoying.
The ridged lip helps provide a tighter seal than many of the other competitors.
The roll-top closure system of the Hydraulic is unique with an interlaced lip. Grooves in the reinforced lip line up and are intended to create a better seal. While it does allow the bag to withstand brief submersion, it lacks the complete protection of a truly interlocking lip like some of the other models we tested.
This model is one of the top scorers in this metric. It is made of a thick and super durable material that can withstand a serious beating. The lash points are also made out of a TPU material and welded into place. Even the backpack attachment points are made of sturdy aluminum.
The backpack straps are held on by metal clips that quick to pop off.
This model is one of the pricier products in this review. With this price, however, comes equally high durability and versatility.
From paddle board to canyon trip, this bag is durable and easy to use.
The Sea to Summit Hydraulic is a versatile hybrid of a dry bag and a backpack. For river trips that also require the occasional use of a backpack, it's a good product. For more serious backpacking, stick to a traditional backpacking pack.