Best Dry Bag for a Boat Day | Ocean Calling Retreats

Two snorkellers swimming beside a sea turtle over a coral reef. Photo: Ocean Calling Retreats.

The little pool of seawater at the bottom of the bag

You climb back up the ladder after a snorkel, reach for your phone, and the bag that said "waterproof" has a little pool of seawater inside. It happens more than people think. Most dry bags do not fail because they were badly made. They fail because of how they were closed, how they were packed, or because they were chosen for a job they were never made for: camera gear sliding across a wet deck, spray coming over the bow, a bag sitting in water at the bottom of the boat.

So what is the best dry bag for a snorkel boat day? Honestly, the brand matters less than three things. How the bag closes (a roll-top, rolled at least three times, is the most forgiving). What it is made of. And whether you use it the way the manufacturer intended. Here is what is worth knowing before you pack.

Why dry bags actually fail

On a boat day a dry bag meets three different threats, and many bags are only built for one of them.

Splash and spray: the boat moves through chop, throwing up mist and the odd wave over the side. Most light dry bags handle this well, even ones that would leak if they went fully underwater.

Submersion: the bag goes into the water. Maybe it fell off the bench during a rough entry, or it sits in a hatch that takes on water. This is where many bags quietly stop being dry bags. Several manufacturers say plainly that some of their roll-top sacks are not meant to be submerged at all.

Abrasion and puncture: boat decks are not gentle. Cleats, fin buckles, a dive knife or the sharp corner of a cooler can pierce thin material long before water pressure is the issue. This is the failure people plan for least.

Knowing which threat you are protecting against changes which bag makes sense. A short snorkel on a calm bay is a different problem from a full day on the boat with rough entries and exits.

What the waterproof rating actually tells you

Ingress Protection (IP) ratings come from the international standard IEC 60529, the same system used for phones, and they sometimes appear on dry bags and phone pouches. The second digit is about water. IPX7 means the item survives temporary immersion, usually to 1 metre for 30 minutes. It does not cover long submersion. IPX8 means continuous immersion beyond 1 metre, but the manufacturer sets the depth and the time, so always read the small print. The "X" simply means dust protection was not rated.

Many dry bag brands do not use IP ratings at all. They prefer their own words, like "waterproof", "submersible" or "for splashes". Read those words as a direction, not a promise. When in doubt, expect less protection than the label suggests, and give a phone or camera you care about a second layer, whatever the tag says.

Roll-top or zip: which closure keeps water out?

The single biggest factor in whether a dry bag holds up on a boat is the closure, not the fabric.

A roll-top dry bag works like this: you push out the extra air, fold the top down on itself several times, then clip the buckle. The folds press against each other and make the seal. Manufacturers such as SealLine and Exped recommend at least three rolls or folds, and NRS asks for at least three folds on its roll duffels. Some guides suggest three to five, and say firm, even rolls matter more than the exact number. Rolling only twice is one of the most common reasons a "dry" bag lets water in. It is a mechanical seal, not a magic one, and it only works if you do it right every time, including with cold, wet hands on a moving boat.

Zipped dry bags rely on a waterproof zip, which is quicker to open. That is also the risk. A zip left half closed "just for a second" is not waterproof at all, and waterproof zips need care to keep working, so follow the manufacturer's advice for cleaning sand and salt out of them.

For a boat day, with lots of opening, salt spray and bags moved around, a roll-top is the more forgiving choice for most people, simply because a bad roll is easy to see and fix. If you are choosing one, we keep a short list of roll-top dry bags in different sizes.

Material: the trade-off nobody explains upfront

Dry bags are mostly made from PVC or PVC-coated polyester (often called tarpaulin), TPU, or TPU-coated nylon. Each one is a trade-off, not a clear winner. Heavy PVC tarpaulin is generally described as the most puncture-resistant, useful on a deck full of hard edges, but it is heavier, stiffer and does not pack down well for travel. TPU and TPU-coated nylon are lighter and softer, which matters when you already carry fins, a wetsuit and a camera. Thin coated nylon depends more on its seams, so it is less happy next to sharp objects.

We could not find independent tests that rank these materials properly, and many online comparisons come from sellers, so take any strong claim with a pinch of salt. In practice, a bag that lives on the boat and gets thrown around is better in a tougher, heavier fabric. A bag that also has to fit in your carry-on is better light. Check the fabric thickness (denier) and the manufacturer's own specifications for your use.

Sizing for what a boat day really needs

Too big is another common mistake. A 20-litre bag looks reasonable in a shop, but it is often more than one person needs for a phone, a small towel, sunscreen and a light layer. A half-empty bag is also harder to roll tightly, because there is more air and loose material in the fold.

As a rough guide: 5 to 8 litres holds a phone, wallet and light layer for one person on a half day. 10 to 15 litres adds a towel and snacks. 20 litres and more makes sense for a full day, for people sharing, or for camera gear in its own padded case. If you carry an action camera or a phone, put it in a small case inside the bigger dry bag. Trusting expensive electronics to one single seal is a bad trade for the weight of a second pouch.

Colour is not decoration

A bright dry bag, yellow or orange or any safety colour, is easier to spot if it goes overboard. It is also easier to find in a pile of black bags at the bottom of the boat, and easier for the crew to count before leaving. It sounds small until a dark bag drifts away on a current over dark water.

Keeping your boat day kind to the ocean

In a small way, a dry bag is also an environmental tool. Things that go overboard on a boat day, a sunscreen tube, a snack wrapper, a cap, do not come back. They become part of the litter we see on so many beaches. Keeping your rubbish sealed in the bag until you are back on land is a simple habit. And one well-made bag that lasts many years, instead of a cheap one every season, means less plastic in the long run.

Think of the reef when you pack what goes inside, too: a mineral sunscreen put on well before you get in the water, and a refillable bottle instead of single-use ones. Our reef-safe packing list covers the rest of the kit.

What actually goes wrong, and the 30-second fix

Most dry bag failures come down to a few habits: an incomplete roll (two folds instead of three or more), a bag packed so full the seal cannot close, a puncture from something sharp packed next to it, and a zip left slightly open. None of these is really the bag's fault. About thirty seconds of attention before the boat leaves fixes them: push out the air, roll at least three times, clip, and check.

None of this replaces good sense on the boat itself. Keep valuables away from the edge, secure your bag before the boat moves, and ask the crew where the dry storage is. A dry bag is a backup, not a guarantee, which is the honest way to think about any piece of gear. For everything else to bring, see our ocean retreat packing list.

If this made you curious about a boat day with us, you can explore our small-group retreats.

Questions people ask

How many times should I roll a dry bag?

At least three times. SealLine, Exped and NRS all ask for a minimum of three rolls or folds before closing the buckle, and firm, even rolls matter more than the exact number.

Can I fully submerge my dry bag?

Only if the manufacturer says so. Some roll-top sacks are clearly labelled as not meant for submersion, and most are designed mainly for splashes and spray. Check the product's own specification.

What do IPX7 and IPX8 mean?

Under IEC 60529, IPX7 means protection against temporary immersion, usually 1 metre for 30 minutes. IPX8 means continuous immersion beyond 1 metre, with the depth and time set by the manufacturer.

What size dry bag do I need for a snorkel boat day?

As a rough guide, 5 to 8 litres for one person's phone, wallet and a light layer on a half day, 10 to 15 litres if you add a towel and snacks, and 20 litres or more for a full day or shared gear.

Is PVC or TPU better for a dry bag?

Neither wins on everything. Heavy PVC tarpaulin is generally tougher against punctures but heavier and bulkier. TPU and TPU-coated nylon are lighter and pack smaller. Choose by whether the bag lives on the boat or travels in your luggage.

Wildlife encounters are never guaranteed and never forced. Ocean Calling works only with vetted, ethical local operators, and every animal is free to approach, or not, entirely on its own terms.

Sources & further reading

Further reading on Ocean Calling: More from the journal · Wildlife & the law · See the retreats · Ocean Atlas

Best Dry Bag for a Boat Day, and How to Keep It Dry