In short: an eSIM for diving trips works the same as in any other destination: it connects you to the local network as soon as you hit land, but underwater, there's no signal with any technology. Actual coverage depends on the destination: excellent in Cozumel or Koh Tao, limited in remote Maldives atolls or Komodo National Park, and non-existent on the open sea during a liveaboard.
The reality of coverage in diving destinations
The world's best diving spots have something in common: they are far from everything. Small islands, sparsely urbanized coasts, marine national parks where it's not feasible to set up antennas. This means that, unlike a European city where any eSIM will give you decent 4G everywhere, on a diving trip, coverage changes radically between the town where you sleep and the pier from which you head out to the reef.
The eSIM doesn't change physics: if there's no antenna in the area, there's no data, no matter which operator you're a customer of. What does change is that you don't have to search for a mobile phone store in Labuan Bajo or Malé to get a local line, nor depend on a physical card that you could lose on the boat. You buy the plan before leaving home, install it with the hotel WiFi on your last night, and upon landing, you already have network without visiting a counter.
Coverage by diving destination
Here's what you'll find in the most sought-after diving destinations. For quick reference, here's how coverage is distributed between the accommodation area and the dive site:
| Destination | Coverage at accommodation | Coverage in diving area |
|---|---|---|
| Cozumel and Riviera Maya, Mexico | Very good, Telcel network well deployed | Good near coast, lost further out at sea |
| Koh Tao and Similan, Thailand | Good in Koh Tao with AIS and DTAC | None in Similan National Park (protected area) |
| Komodo (Labuan Bajo), Indonesia | Good in Labuan Bajo with Telkomsel | Very limited among the park's islands |
| Raja Ampat, Indonesia | Acceptable only in Waisai and Sorong | Practically non-existent in the archipelago |
| Maldives (resort islands) | Good on main islands, Dhiraagu and Ooredoo | Limited in remote atolls |
| Great Barrier Reef, Australia | Very good in Cairns and Port Douglas | Cut off a few miles from the coast |
| Red Sea, Egypt | Good in Hurghada, Sharm el Sheij and Dahab | Drops rapidly to the south, in the desert and on cays |
| Philippines (Malapascua, Moalboal) | Good on the coast with Globe and Smart | Lost on the boat trip to the dive site |
A pattern repeats in all these destinations: the signal is a last-mile problem, not an entire-country one. You can have perfect 4G at your Labuan Bajo hotel and lose it as soon as the boat leaves the harbor for Komodo National Park. If you go to San Andrés or Providencia in Colombia, the pattern is identical: good network in town, much worse in the surrounding cays.
Liveaboards and dive boats: what to really expect
If your trip includes a liveaboard (those boats where you sleep for several days doing consecutive dives), assume you'll be disconnected most of the time. On the open sea, there's no terrestrial antenna to rely on, whether your phone has an eSIM or not. Some large boats offer satellite Wi-Fi, but it's usually slow, expensive, and intended for occasional messages, not for working or video calls.
The eSIM is useful in this context for port days: before boarding, when the boat stops at an island with a town, or when disembarking. Don't buy it thinking you'll have data in the middle of the Flores Sea or the open Red Sea, because it won't happen, and it's not a problem with your operator but with the lack of antennas to reach there.
How many GB does a diver really need?
Here's a little-discussed advantage: a diving trip consumes less data than a normal urban trip. You spend hours in the water, on the boat, or sleeping early for the 7 AM dive, so your phone is off or in airplane mode for much of the day. A plan designed for 8-10 days of diving with moderate use (messaging, photos, uploading a story at night at the hotel) is usually more than enough without needing to contract the largest plan in the catalog.
If you're also going to keep dive logs with apps that sync profiles to the cloud, upload them at night with the resort's Wi-Fi instead of using mobile data: most of these apps allow you to log the dive offline and sync later. And check our guide to data-saving tips for travel if you want to stretch the smallest plan without running out in the last few days.
How to activate your eSIM before diving
- Purchase your destination plan on purasim.com before leaving Spain, allowing a couple of days.
- Install the profile (the QR) using home or airport Wi-Fi; never leave this until the last minute with poor coverage.
- Leave the eSIM installed but deactivated until you land, to avoid inadvertently incurring roaming charges.
- Upon landing, activate mobile data for the eSIM from Settings and confirm that your Spanish line is for calls only if you need it.
- If your route passes through several islands or countries on the same trip, check if a multi-destination plan is more cost-effective before buying one for each stop.
One detail that many people miss: in some remote dive resorts, the hotel Wi-Fi is so poor (or so expensive) that in practice, you'll rely more on your eSIM than on the accommodation's network. Before you go, check the resort's website for any mention of connectivity; if they don't say anything, it's a good sign that their connection isn't good. And if you've never activated an eSIM, it's a good idea to review the how to install an eSIM guide step-by-step beforehand.
eSIM, local SIM or roaming: what is best for a diving trip
| Option | Management | Fits a diving trip |
|---|---|---|
| Roaming from your Spanish operator | None, works automatically | Cost skyrockets outside the EU; bad for long trips |
| Local physical SIM | Requires finding a store and sometimes documentation | Complicated on small islands without an operator store |
| PuraSIM eSIM | 100% digital, bought and installed before leaving | Avoids relying on finding a store at the destination |
Here's where it's important to be honest: if your diving getaway is a weekend in the Balearic Islands or on the Spanish Mediterranean coast, you don't need to buy anything; your national plan already covers you. It also doesn't make much sense if you're going to a destination where you'll spend 90% of the time on a boat without coverage anyway: in that case, activating data only on arrival and departure days might be enough, and you don't need the largest plan in the catalog. Where it does pay off: any destination outside the EU where you'll be spending several days on land between dives, moving between islands, or simply where you don't want to risk finding a mobile phone store in a fishing village. If your route combines diving with a country for which we already have a specific guide, such as Australia and New Zealand or Peru, also check that guide as it goes into more detail about the country itself.
What almost no one tells you about eSIMs in diving destinations
Underwater, there is no signal with any operator or any technology. It sounds obvious, but every season someone asks if an eSIM will give them coverage during a dive. Water blocks the frequencies used by mobile networks; not even the most powerful operator in the world can solve this. What does exist are independent diving GPS beacons for surface emergencies, which have nothing to do with your phone's SIM.
The village with the resort is not representative of the entire diving area. In Raja Ampat, for example, decent coverage is in Sorong (the mainland city from which the ferry departs) and in Waisai, but as soon as you enter the archipelago, the signal practically disappears, even if your resort has its own satellite Wi-Fi. Activate your eSIM in Sorong before taking the boat; don't wait until you're already on the island.
Marine national parks often have poorer coverage by design, not by chance. Areas like Similan in Thailand or Komodo National Park restrict infrastructure to protect the environment, so it's not a network failure; it's the norm for the area. If you need to be reachable for work during those days, notify beforehand that you will be out of coverage.
The boat trip to the dive site is when most people lose signal without realizing it. In the Philippines or Indonesia, it's common to leave the pier with perfect 4G and lose it within a few minutes of sailing. If you need to send an important message or download something, do it before getting on the boat, not on the way.
Download offline maps and your hotel reservation before leaving the big city. On remote dive islands, even if you have data, the speed can be so slow that loading Google Maps on the spot feels endless. Download the map of the area in advance, with Wi-Fi, and save yourself the frustration at the departure pier.
Conclusion
For a diving trip, the eSIM solves the same old problem: arriving connected without queues or paperwork, without having to find an operator store in a small town. What it cannot solve, because it cannot, is coverage where there are no antennas: on the high seas, underwater, or in the heart of a protected marine park. Buy the plan according to the days you will spend on land between dives, activate it before leaving home, and assume that on the boat you will disconnect, which is also a reason to travel for diving.
Frequently Asked Questions
Is there coverage on diving liveaboard boats?
When the boat is in port or near the coast, usually yes. On the open sea, without any terrestrial antenna within reach, there is no 4G with any operator, whether you have an eSIM or a physical SIM. Some liveaboards offer satellite Wi-Fi as an alternative, but it is usually limited and costs extra.
Does eSIM work in Koh Tao, Thailand?
Yes, Koh Tao has good 4G coverage from AIS and DTAC along most of the coast. It is lost in Similan National Park, further north, if your diving route includes that area.
Does eSIM work in the Maldives?
In resorts on the main islands, there is coverage from Dhiraagu and Ooredoo Maldives. In more remote atolls further from the capital, coverage can be limited or non-existent, so it's advisable not to rely on constant data if your trip goes to those areas.
How many GB does a diver need for a 10-day trip?
With moderate use (messaging, photos, occasional queries), less data is usually sufficient than you would use on an urban trip, because many hours are spent at sea or on the boat without coverage. Adjust the plan to the actual days you will be on land with a signal, not the total days of the trip.
Does eSIM work in Komodo, Indonesia?
In Labuan Bajo, the city from which boats depart, there is good 4G coverage from Telkomsel. In the islands of Komodo National Park, coverage is very limited, so make sure you have important things downloaded before setting sail.
Can I use eSIM to call in an emergency during a dive?
No. Your mobile phone has no signal underwater with any technology, regardless of your operator. Dive safety depends on the dive center's protocols and specific emergency equipment, not on your phone.
Is it worth buying an eSIM if my diving trip is just a weekend in Europe?
It depends on the destination: if it's within Spain, you don't need anything, your national rate already covers you. If it's a diving weekend in another European country, for very short stays within the EU, sometimes the roaming included in your rate is already enough, so don't rush to buy anything without checking first.
