The simplest reliable way to keep your phone dry while paddling is a small roll-top dry bag, clipped where you can see it, with the top rolled down at least three times. A 2 liter is plenty for a phone, a key, and a card. A waterproof case works too if you want to shoot photos. A ziplock is a backup, not a plan.
Everyone has a story about the phone that did not make it. The good news is this is a solved problem, and the solution is inexpensive and small enough that there is no reason to keep gambling. Here is the honest version, including when a dry bag is not the right answer.
Why a small dry bag is the easy answer
A 2 liter roll-top holds your phone and the couple of things you never want to swim after. You roll the top down three times, clip it to a deck line or your PFD, and forget about it. It keeps spray, rain, and the splash of a wet re-entry off your phone, which is what actually happens to it on a normal paddle. Keep it clipped in and keep it closed and it does its job.
One caveat worth saying plainly: a roll-top dry bag is built to keep water out in real paddling conditions, not to be a deep-water dive case. Do not treat it as something you can sink and swim with for minutes at a time. Clip it in, roll it right, and it will keep your phone dry through the day.
When a waterproof phone case is the better pick
If the whole point is to use your phone on the water, to shoot the flat morning or check a map, a waterproof case beats a bag, because you can touch the screen through it. Look for one you can operate without taking the phone out, since the moment you unbag a phone over the water is the moment you drop it. A case and a small dry bag are not rivals. Plenty of paddlers carry the case for photos and the 2 liter for the key, the card, and the snack.
What about a ziplock?
A zip-top freezer bag will keep rain and spray off a phone in a pinch, and it is better than nothing on a day you forgot your kit. It is not a system. It punctures, it works loose, and it offers no protection if it goes in the water. Use it as a backup, not as the thing you rely on all season.
The short version
Clip a small dry bag where you can see it, or use a touchscreen-friendly case if you want to shoot. Keep it closed, keep it close. Browse the 2 liter prints and pick the one you will actually notice when it is time to clip it in.
Frequently Asked Questions
Will a dry bag really keep my phone dry while paddleboarding?
Yes, when it is rolled and clipped correctly. Roll the top down at least three times, clip it to a deck line or PFD, and it keeps spray, rain, and splash off your phone through a normal paddle. Keep it closed and keep it in the boat.
What size dry bag is best for just a phone?
A 2 liter. It fits a phone, a key, a card, and a small snack, with enough room to roll the top for a real seal. It is small enough to clip out of the way and stay there.
Is a dry bag or a waterproof case better for my phone?
A dry bag if you mainly want to keep the phone stowed and safe. A waterproof case if you want to use the screen on the water, since you can touch it through the case. Many paddlers carry both.
Can I fully submerge a roll-top dry bag with my phone inside?
Treat it as splash, rain, and short-exposure protection, not a dive case. Keep it clipped in and closed. It is built to keep water out during normal paddling, including a flip or a quick swim, not to be sunk on purpose.
Does a ziplock bag work for a phone on the water?
As a backup, yes. It keeps rain and spray off in a pinch. It is not reliable long term because it punctures and works loose, and it offers no protection if it goes in the water. Carry a real dry bag or case for anything you care about.