Sea to Summit Lightweight Dry Bag 20L review
By Tom Calder
A properly made 20-litre roll-top dry bag that weighs about 95g and keeps kit dry through heavy rain, with taped seams and a lifetime guarantee. It is a liner rather than a bag in its own right, but for protecting an emergency kit inside another bag it is hard to fault.
- Best for
- Waterproofing the contents of a grab bag or rucksack — documents, electronics, spare clothes and a first-aid kit.
- Skip it if
- You want a standalone grab-and-go bag
as of 2 Nov 2026, 13:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.We earn a commission if you buy through the retailer links on this page. It doesn't change our verdict. How we make money →
Researched, not used. We haven't used this product. This review is built from the maker's specifications, owner reports and our own sizing.
What we like
- Reliably waterproof: TPU-laminated 70D ripstop nylon, fully taped seams and a Hypalon roll-top
- Very light (~95g) and packs down to almost nothing when not in use
- Durable for its weight class, with Sea to Summit's lifetime guarantee behind it
Worth knowing
- No straps or handles — it has to live inside or clip onto another bag
- Roll-top closure resists rain and splashes, not prolonged submersion
ⓘ As an Amazon Associate, PreparedBritain earns from qualifying purchases. We may earn a commission when you buy, or a fee when you request a quote, through our links. When two products are close, commission can decide which one we pick. A clearly better product always wins. Amazon prices come from Amazon's own product data and show the date and time they were retrieved. Prices at other retailers are checked by us, less often. Prices and stock can change at any time, so always check the retailer's price before you buy.
Our review
Sea to Summit's Lightweight Dry Bag is a 20-litre roll-top liner that keeps what is packed inside a grab bag or day pack dry in heavy rain, at 91 g. It is the cheap, simple way to protect documents, spare clothes, a first aid kit and electronics inside another bag. It has no straps, and like any roll-top it isn't meant to go under water.
What it is
A tall roll-top bag of recycled 70-denier nylon, bluesign approved, with a polyurethane coating inside, a PFAS-free water-repellent finish outside and seams that are double-stitched and fully taped. The 20-litre size is 23.4 by 27.1 cm across the oval base and 47.8 cm tall when rolled three times, and weighs 91 g. The UK page describes a non-wicking Hypalon roll-top closure secured with a buckle.
Sea to Summit makes the same bag in several sizes and colours, so you can colour-code a kit: one for documents and chargers, one for clothes, one for first aid.
Why it belongs in a grab bag
Many rucksacks and holdalls let water in at the seams and zips in sustained rain, and a soaked change of clothes or a wet passport is a real problem when you have had to leave home. Lining the bag with a dry bag, or packing the important things into one, solves that for very little weight. The government's Be Ready checklist asks for copies of IDs and documents, blankets and warm clothing; those are exactly the things worth keeping dry.
It is also useful at home in a flood: important papers and a phone charger can go into a rolled dry bag on an upstairs shelf. Our flood preparation checklist covers what else to move.
The limits
Sea to Summit is plain about this: avoid submersion, because water can seep through the roll-top closure of any dry bag. The UK page describes it as waterproof where the bag won't be submerged. So it is a rain and splash bag, not one for being dragged under water in a capsize.
The two Sea to Summit sites also quote different waterproof ratings for the fabric, so we don't repeat either. There are no shoulder straps or handles, so it always needs another bag to live in.
How it compares
On our grab bag comparison, this is the accessory rather than the bag. The EVAQ8 family grab bag gives you a holdall full of kit, and a dry bag inside it keeps the sleeping bags and documents dry. The Lifesystems Survival Shelter 2 packs small enough to sit inside this bag with room to spare. For documents alone, a fireproof or waterproof document pouch from our document bag page is a flatter fit.
Our verdict
A light, well-made and inexpensive way to keep the important parts of an emergency kit dry. Buy one or two for any grab bag. If you need a bag to carry on its own, buy a rucksack and use this inside it.
A researched review, built from the maker's specs, manual and UK listings; facts checked 2 Nov 2026. Sources: Sea to Summit: Lightweight Dry Bag; Sea to Summit UK: Lightweight Dry Bag; GOV.UK Be Ready: emergency checklist.
Who shouldn't buy this
You want a standalone grab-and-go bag — this has no carry straps. Buy a rucksack for that job and use this inside it; or if you only need cheap organisation rather than waterproofing, a £3 zip-lock approach will do.
Key specs
| Covers | — |
| Duration | — |
| Items | 1 |
This is a Researched review: we haven't used this product. We check every specification against at least two independent sources, re-check the UK price on a schedule where we can track it automatically, and say plainly who it isn't for. Commissions never change a rating.
If this isn’t the one
Best for A lightweight warmth-and-shelter layer for a car kit or grab bag when two people are caught out in bad weather.
as of 2 Nov 2026, 13:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.
Best for A reusable emergency bivvy for a car, walking pack or grab bag where cold and wet are real risks.
as of 2 Nov 2026, 13:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.
Best for Drivers who want one grab-and-go bag covering both a roadside breakdown and a cold-weather wait.
as of 2 Nov 2026, 13:07 GMT · Details
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.co.uk at the time of purchase will apply to the purchase of this product.Questions
Is the Sea to Summit Lightweight Dry Bag waterproof?
The fabric and taped seams are waterproof, but Sea to Summit says to avoid submersion because water can seep through the roll-top closure of any dry bag. It is designed for rain and spray.
How heavy is the 20-litre Lightweight Dry Bag?
Sea to Summit gives 91 g for the 20-litre size, which is 47.8 cm tall rolled three times and 23.4 by 27.1 cm across the base.
How do I close a roll-top dry bag properly?
Push the air out, fold the top over itself at least three times, then clip the buckle. Sea to Summit's sizes are measured rolled three times.
What should I pack in a dry bag in a grab bag?
The things that are useless wet: copies of ID and documents, a phone charger or power bank, a first aid kit, a spare set of warm clothes and a blanket or sleeping bag. Keep the heaviest items low in the outer bag.
Free alerts for your home
Home Alerts emails you when a power cut, a Met Office warning or a flood warning covers your postcode. Free for your own home. Sign up in a minute.
Start free →