So the Sea to Summit Big River Dry Bag—specifically the 8-liter one—is solid when it comes to dealing with rain, splashes, and most of the usual wet stuff you run into during activities like kayaking or hanging out on a boat deck.
It's got a 10,000mm waterhead rating, according to the manufacturer's description, which is pretty strong for keeping water out when it's not fully submerged. But keep in mind it's not made for going underwater completely.
From what we've found, this is more than just a manufacturer precaution. People who've used it often say it does a great job keeping things dry in rainy conditions or when attached to a kayak.
Its fabric is tough 420D nylon with a TPU coating, which can handle rough environments and keep things from soaking—as long as the bag itself isn't submerged. The seams are reinforced too, so a bit of rain isn't going to get inside.
However, if you decide to dunk it underwater, water might start to seep in eventually. Some folks have mentioned minor leaks when it was submerged, and that's backed up by professional reviews emphasizing it's not meant for diving into the water.
To get the best out of its water-resistance, make sure you roll the top tightly at least three times before clipping it shut. That's pretty important for keeping your stuff dry inside.
If you expect the bag to go underwater often, you might want to check out dry bags made for full submersion—they're out there if you need them.
In short, if you want something durable and reliable for keeping gear dry above water, the Sea to Summit Big River Dry Bag is a good pick. Just be aware of its limits with full submersion and think about what you need in a dry bag before choosing.
