You have just capsized your kayak in a Welsh river and watched your phone, wallet, and car keys float downstream inside a rucksack that was definitely not waterproof. Or maybe nothing that dramatic — you just left your bag in the bottom of a sit-on-top kayak and the constant splashing soaked everything inside. Either way, you are standing on the bank holding a dripping bag of ruined electronics and soggy sandwiches, wishing you had spent £8 on a dry bag before you left the house.
In This Article
- What Is a Dry Bag?
- How Dry Bags Work
- Types of Dry Bag
- Choosing the Right Size
- Material and Durability
- Waterproof Ratings Explained
- How to Seal a Dry Bag Properly
- Dry Bags for Different Activities
- Best Dry Bags by Budget
- Common Dry Bag Mistakes
- Frequently Asked Questions
What Is a Dry Bag
A dry bag is a waterproof sack with a roll-top closure designed to keep your gear dry in wet environments. They are used by kayakers, paddleboarders, sailors, wild swimmers, hikers, cyclists, and anyone who needs to protect belongings from water, rain, or spray.
The concept is simple — you put your stuff inside, roll the top down at least three times, clip the buckle, and the contents stay dry even if the bag is submerged. Unlike a regular rucksack with a rain cover (which leaks at seams and zips), a dry bag has welded seams and no zips at all. The only opening is the roll-top, and when sealed correctly, it is completely watertight.
Why Regular Bags Fail
Zips leak. Stitched seams wick water. Rain covers blow off in wind and pool water on top. Even “water-resistant” backpacks will soak through in sustained rain or if dropped in water. A dry bag eliminates all of these failure points. Our kayak buying guide mentions dry bags as essential kit, and for good reason — water and electronics do not mix.
How Dry Bags Work
The Roll-Top Seal
The top of a dry bag is a wide opening with a flat closure strip. You fold the opening over itself at least three times (creating multiple layers of sealed material), then clip the buckle to hold it shut. This creates a compression seal that prevents water entering from above.
The key is the multiple folds. One fold is not enough — water can work its way through a single fold under pressure. Three folds creates a seal that will survive full submersion in most conditions.
Welded Seams
Unlike stitched bags where thread punctures the fabric (creating tiny water channels), dry bag seams are welded — the material is bonded using heat or radio frequency, leaving no holes. High-quality dry bags have fully welded seams throughout. Budget bags sometimes have welded main seams but stitched attachment points (for straps and D-rings), which can be weak spots.
Air Trapping
When you roll a dry bag closed with air inside, the trapped air creates buoyancy — the bag floats. This is a deliberate feature. If you capsize and lose your dry bag, it floats on the surface where you can retrieve it. Squeeze out most of the air before sealing for easier packing, but leave a small amount for flotation insurance.
Types of Dry Bag
Standard Roll-Top Dry Bag
The classic design. A simple waterproof sack with a roll-top closure, one main compartment, no pockets. Available from 1 litre to 60+ litres. This is what most paddlers use and what you should start with.
- Best for: Kayaking, canoeing, SUP, general water sports
- Price range: £5-30 depending on size and material
Dry Bag Backpack
A dry bag with padded shoulder straps, allowing you to carry it like a rucksack. Some have external pockets (these pockets are usually not waterproof — check before assuming). Popular with bike commuters and wild swimmers who need to walk to and from the water.
- Best for: Walking to launch sites, bike commuting in heavy rain, wild swimming
- Price range: £20-60
Dry Bag Duffel
Larger capacity (40-90 litres) with handles and sometimes a shoulder strap. Used for multi-day trips where you need to pack camping gear, clothing, and food. These are the workhorses of expedition paddling.
- Best for: Multi-day kayak trips, sailing, expedition canoeing
- Price range: £30-80
Phone-Sized Dry Pouch
A small transparent pouch that fits a phone and allows touchscreen use through the material. Essential for navigation and photography on the water. Typically rated IPX8 (submersible to 10-30 metres).
- Best for: Keeping your phone accessible and dry while paddling
- Price range: £5-15
Compression Dry Bag
A dry bag with compression straps that squeeze out air and reduce the packed volume. Useful for clothing and sleeping bags where you want waterproofing and compactness.
- Best for: Backpacking, camping, storing clothes and sleeping bags
- Price range: £10-25
Choosing the Right Size
1-5 Litres
Phone, wallet, keys, and a snack. Enough for a short paddle where you are not carrying much. The 2-litre size is perfect for a phone pouch plus a few small items.
5-10 Litres
A change of clothes, towel, and lunch. The ideal size for a day paddle or a trip to the beach. I keep a 10-litre bag permanently packed with a dry set of clothes in the car for after-paddle changes — it has saved me from several soggy drives home.
10-20 Litres
A full day’s kit including food, spare clothing, first aid kit, and electronics. Good for day trips where you need more than the basics. This is the most versatile size range — our paddle guide recommends this capacity for day outings.
20-40 Litres
Overnight trip capacity. Enough for a sleeping bag, spare clothes, cooking kit, and food for one night. Used as a main pack for lightweight wild camping or as one of several bags on a multi-day paddle.
40-60+ Litres
Multi-day expedition capacity. Full camping kit, multiple days of food, extensive gear. Usually a duffel format at this size.
The Multiple Bag Strategy
Experienced paddlers rarely use one big dry bag. Instead, they use several smaller bags:
- A 5-litre bag for electronics and valuables (phone, wallet, keys, camera)
- A 10-litre bag for clothing
- A 15-litre bag for food and cooking kit
- A 2-litre pouch for items needed during the paddle (snacks, sunscreen, phone)
This approach means if one bag leaks, you do not lose everything. It also makes packing and unpacking easier — you know exactly which bag contains what.
Material and Durability
PVC (Polyvinyl Chloride)
The most common material for budget and mid-range dry bags. Heavy but very durable and fully waterproof. PVC bags feel thick and rubbery. They resist abrasion well (important when loading bags into kayak hatches) and are easy to wipe clean.
- Thickness: Usually 250-500 denier
- Pros: Cheap, tough, waterproof, easy to clean
- Cons: Heavy, not eco-friendly, can feel sticky in heat, not breathable
- Common brands: OverBoard, Aqua Quest
TPU (Thermoplastic Polyurethane)
A more modern material used in premium dry bags. Lighter than PVC, more flexible, and more environmentally friendly. TPU bags feel smoother and less rubbery.
- Thickness: Usually 210-420 denier
- Pros: Lighter, more flexible, better cold-weather performance, more eco-friendly than PVC
- Cons: More expensive, less abrasion-resistant than thick PVC
- Common brands: Sea to Summit, Exped, Ortlieb
Nylon with PU Coating
Lightweight nylon fabric with a polyurethane waterproof coating on the inside. The lightest option, used by ultralight hikers and backpackers. Not as robust as PVC or TPU — the coating can degrade over time with heavy use.
- Pros: Very light, packable, soft
- Cons: Coating degrades with use (2-3 years of heavy use), less abrasion-resistant, seam sealing can fail
- Common brands: Alpkit, Lomo
Waterproof Ratings Explained
IPX Ratings
Dry bags and pouches often carry an IPX rating:
- IPX4 — splash-resistant. Fine for light rain, not submersion
- IPX6 — resistant to powerful water jets. Survives heavy spray and rain
- IPX7 — submersible to 1 metre for 30 minutes. Survives a capsize
- IPX8 — submersible beyond 1 metre (manufacturer specifies depth). Survives extended submersion
For paddling, you want at least IPX7. Phone pouches should be IPX8. The British Standards Institution maintains the IP rating system — the numbers are standardised, not marketing claims.
What the Rating Does Not Tell You
An IPX8 pouch will keep water out when submerged, but it will not survive a sharp rock puncturing the material. The rating measures water resistance, not physical durability. A cheap IPX8 phone pouch from Amazon will keep water out but may tear if snagged on a branch. A premium one uses thicker material that resists both water and physical damage.
How to Seal a Dry Bag Properly
Getting this wrong is the most common reason dry bags “fail.” The bag is not leaking — the user sealed it incorrectly.
Step-by-Step
1. Open the bag and place your gear inside, leaving at least 15-20cm of empty material above the contents 2. Squeeze out excess air by pressing the bag from the bottom upward (leave a small amount for flotation) 3. Fold the opening flat, ensuring the two sides of the closure strip are aligned 4. Roll the flat opening down toward the contents — at least three full rolls 5. Clip the buckle to secure the roll 6. Give the bag a gentle squeeze — if air escapes, the seal is not right. Unroll and redo
Common Sealing Mistakes
- Only rolling once or twice — three rolls minimum. Four is better
- Rolling with creases — the closure strip must be flat before rolling. Creases create channels where water can enter
- Overpacking — if the bag is stuffed full, there is not enough material above the contents to create a proper roll. Never fill a dry bag more than 75% of its stated capacity
- Rolling with the wrong side out — the waterproof coating is on the inside. If you fold the opening outward instead of inward, the seal is less effective
Dry Bags for Different Activities
Kayaking and Canoeing
The core use case. You need bags that fit inside kayak hatches or can be strapped to canoe thwarts. Standard roll-top bags in 5-20 litre sizes work best. Bright colours (orange, yellow) are preferable — if a bag goes overboard, you need to spot it quickly on the water. Our kayak guide covers how different hull shapes affect storage capacity.
Stand Up Paddleboarding
SUPs have limited deck space. A 10-litre dry bag bungeed to the front of the board handles most day trips. A phone pouch on a lanyard around your neck keeps your phone accessible. Avoid anything too heavy — it affects board stability.
Wild Swimming
You need a bag that floats prominently (bright colour, inflated with some air) so you can tow it behind you or spot it from the water. A 20-litre dry bag backpack is the classic wild swimmer’s choice — walk to the spot wearing it, leave your clothes inside at the water’s edge or tow it while swimming.
Cycling and Commuting
Dry bag backpacks are increasingly popular with UK bike commuters. Ortlieb, Alpkit, and Lomo all make cycling-specific dry bags with reflective elements, padded straps, and helmet attachment points. In British weather, a genuinely waterproof bag beats a rucksack with a rain cover every time.
Hiking and Camping
Use dry bags inside your rucksack as liner bags — one for clothes, one for sleeping bag, one for electronics. This protects against both rain leaking through and the inevitable river crossing where the rucksack takes a dunking. Compression dry bags are ideal here because they reduce packed volume.
Best Dry Bags by Budget
Under £10
- Lomo 10L Roll-Top Dry Bag (about £6-8, from Lomo directly or Amazon) — a Scottish company making solid budget dry bags. PVC, welded seams, basic but effective. Available in multiple sizes and colours. This is the bag I recommend to every beginner paddler — it costs less than a pub lunch and does the job
- Unigear 5L/10L/20L (about £7-9, Amazon) — decent budget option in multiple sizes. PVC, adequate seam welding
£10-25
- Alpkit Gourdon (about £12-18, from Alpkit directly) — British brand, excellent quality for the price. TPU-coated nylon, lighter than PVC bags. Available in 2L to 20L. Alpkit is based in Nottingham and their customer service is brilliant
- Sea to Summit Lightweight Dry Sack (about £15-20, from Cotswold Outdoor or GO Outdoors) — ultralight nylon construction, perfect for backpacking. Not as tough as PVC for kayaking but ideal when weight matters
£25-50
- OverBoard Pro-Vis Waterproof Backpack 20L (about £35-45) — dry bag backpack with high-vis panels and reflective elements. Popular with commuter cyclists. Comfortable straps, proper roll-top seal
- Ortlieb PS10 Series (about £15-35 depending on size) — German engineering. Ortlieb dry bags are the industry standard for durability. The PS10 uses lightweight PVC-free material and has been a staple in the paddling community for decades
£50+
- Ortlieb Velocity PS 23L (about £70-85) — the premium cycling dry bag backpack. Fully waterproof, comfortable for all-day carrying, reflective, with laptop sleeve. Expensive but built to last a decade
- Sea to Summit Hydraulic Dry Pack 35L (about £60-70) — expedition-grade dry bag backpack with proper harness system. For serious multi-day trips
Common Dry Bag Mistakes
Trusting a Zip-Lock Bag for Electronics
Sandwich bags and zip-lock bags are not waterproof. They resist splashes but will flood under submersion. Your phone belongs in a proper IPX8 dry pouch or inside a roll-top dry bag — not in a freezer bag with a hopeful seal.
Leaving Sharp Objects Inside
Keys, karabiners, tent pegs, and multi-tools can puncture dry bags from the inside. Put sharp items in a small stuff sack or wrap them in clothing before putting them in the dry bag.
Not Testing Before You Need It
Fill your dry bag, seal it, and submerge it in a bathtub or sink for five minutes before your first trip. Check for leaks at seams and the closure. It is better to discover a defective bag at home than on a river in Wales.
Storing Wet
After use, open the bag and let it dry completely before storing. Storing a sealed wet dry bag breeds mould inside — you will open it for your next trip to find a science experiment.
Assuming “Waterproof” Means Indestructible
Dry bags keep water out but they are not armour. Dragging a PVC dry bag across rocks will eventually wear through the material. Treat them with reasonable care and they last years. Abuse them and they fail.
Frequently Asked Questions
How waterproof are dry bags really? A quality dry bag with welded seams, sealed correctly with three or more rolls, will keep contents dry through full submersion. The roll-top closure is the critical point — if sealed properly, the bag itself will not leak. Most “dry bag failures” are user error in sealing.
Can I use a dry bag as a pillow when camping? Yes — stuff it with spare clothes, seal it with air inside, and it makes a surprisingly comfortable camping pillow. The waterproof material means it will not absorb ground moisture either.
How do I clean a dry bag? Rinse with fresh water after saltwater use. For stubborn dirt or mould, use a mild soap solution and a soft cloth. Never machine wash. Turn it inside out periodically to dry the interior. Store open and flat.
Do I need a dry bag for kayaking? If you are bringing anything that cannot get wet — phone, wallet, keys, spare clothes, food — then yes. Even on calm water, splashing from paddle strokes will soak anything in an open cockpit or on a SUP deck.
What size dry bag for a phone? A 1-2 litre bag fits a phone plus wallet and keys. For touchscreen use while paddling, get a dedicated phone pouch (about £8-12) instead — these are transparent and allow screen interaction through the material.