Gear

Dry bag (waterproof pack sack)

Three dry bags in different sizes stacked on the deck of a sea kayak

Waterproof pack sacks keep the sleeping bag dry in the bow and the phone dry in your pocket. Here is how to make sense of volumes, materials and roll-top vs zip — and why you usually need more than one.

A dry bag is a pack sack that keeps the water out. You roll the opening down three or four times, click the buckle, and the contents will survive the bag ending up in the sea, lying in a wet cockpit, or having rain over it for a whole day. For paddling it is basic kit — anything that must not get wet has to go into a sack that holds.

There are two things to grasp: how many sacks you need, and which type suits which contents. Most paddlers end up with three to five dry bags spread across different sizes, not one large one.

How many and how large

The standard volumes are 5, 10, 20 and 35 litres, and they match different packing purposes:

  • 5 litres — phone, wallet, charger, bandages. The small sack that sits within easy reach in the cockpit or deck bag.
  • 10 litres — extra layers, hat, mittens, a light lunch. Also works as a food sack for a day trip.
  • 20 litres — the sleeping bag on its own, or clothing for one day.
  • 35 litres — the sleeping bag together with a sleeping mat, or a larger amount of clothing for several days.

For a typical sea-kayak trip with an overnight stay you usually end up with three to five sacks: one for the sleeping bag, one for clothing, one for food, one for electronics and one for first aid. It is not about being tidy for its own sake — it is that if one sack leaks, you do not lose everything.

Materials and their uses

The fabric in the dry bag determines both how long it lasts and how wet it can stand to get.

TPU (thermoplastic polyurethane) is the most robust material. Welded seams, often transparent or semi-transparent, and stays sealed even when submerged in water. TPU sacks from brands such as Ortlieb and Sea to Summit will take decades of use and are the right choice for the sleeping bag and electronics — the things that really must not get wet.

PU-coated nylon or polyester (PU for short) is the most common material in the mid-range. It seals out spray and rain, but cannot stand being left submerged over time. Lighter and cheaper than TPU. Fine for clothing, food and anything that does not need absolute waterproofing.

Lightweight ripstop nylon with PU is the lightest and least robust type — intended for packing inside the rucksack, not for direct contact with water. Used more on hikes than on paddling trips.

For paddling, TPU or good PU-nylon are the main options. Lightweight ripstop is too light — seams let go, and the sack punctures quickly on a sharp edge in the kayak hatch.

Roll-top vs zip

There are two closing principles:

Roll-top is the standard. You fold the opening down three or four times and click the buckles together. Simple, no mechanism that can fail, and the water does not get in as long as the folds stay put. The downside is that the sack is a little more fiddly to open and close on the move.

Waterproof zip is found on some sacks and deck bags. Quicker to open, but the zip needs maintenance (lubricant once a year) and can fail over time. Used mostly on day-use sacks that you open and close many times.

For paddling, roll-top is what works best. The zips from Aquapac and similar are sealed, but they are a mechanism that can fail — and once it fails, the sack is no longer a dry bag.

Specific brands and price level

The market is mature and the products fairly alike. Some brands worth knowing about:

  • Sea to Summit — Australian, a large range in all volumes, both TPU and PU-nylon. Bright colours so they are easy to spot in the rucksack.
  • Ortlieb — German, known for boat bags and document pouches in thick TPU. Robust, expensive, last a long time.
  • Helly Hansen Watersport — Norwegian, good white/orange signal colours, well distributed.
  • Exped, NRS, SealLine — all solid and close to one another in quality.

Price level:

  • 200–600 kr per sack, depending on volume and material. A 20-litre PU-nylon sits around 300 kr; a 20-litre TPU around 500 kr.
  • 400–1200 kr for a set of three or four sacks in different sizes. Sets are often cheaper per sack than buying individually.

For anyone who paddles regularly, two TPU sacks (sleeping bag and electronics) plus two or three PU sacks are the sweet spot. You do not need to replace everything at once — build the collection over a few seasons.

Not the same as a waterproof hatch

Many paddlers assume that the waterproof bulkheads (skott) in the bow and stern make dry bags unnecessary. That is not the case. The hatches seal reasonably well, but no hatch is completely sealed over time. Saltwater and UV break down the seals, and a hatch that was sealed last year may let in several decilitres on a choppy trip this year.

The dry bag is the second layer that protects the contents regardless of whether the hatch leaks. It is the same logic that lies behind all redundant safety equipment on the water — you do not assume that one thing holds, you make sure that two things hold.

Maintenance

Dry bags need little, but some:

  • Rinse with fresh water after saltwater. Salt wears on welded seams over time.
  • Dry it open and inside out before you put it away. Mould grows in sacks that are packed wet on the inside.
  • Check seams and buckles before each season. A split seam can be sealed with seam sealant (Seam Grip or similar), but a sack that leaks in several places should be retired.
  • The roll-top buckles take a lot, but the stiff plastic parts can crack in the cold — handle them with a little care in winter.

A good TPU dry bag lasts 10–15 years with normal use. PU-nylon comes in at 5–10 years.

Next steps

Learn more

Text: Snuitide (2026).