Swept Away by a Current? How to Choose from 4 Marine Rescue Devices — for Both Scuba and Freediving!

There are many water-activity rescue devices on the market — but which one is right for you, and how does each one actually work? Chances are, plenty of people have bought one without ever learning how to use it properly, only to find out too late when an accident strikes. Dive safety is a fundamental concept that every water-activity operator and enthusiast should have. In this article, the Editor shares how to choose from the 4 most common marine rescue devices available in Taiwan!

How to choose from 4 rescue devices — so you can stay calm and respond effectively when an accident happens

What Does It Feel Like to Be Swept Away by a Current?

Whether you're scuba diving or freediving, being carried off by a current is something that can happen to anyone. Since the Editor primarily dives scuba, the following account is based on personal experience of being swept away — and we'd love to hear from any freedivers who've had their own drifting stories to share. Some might wonder: isn't drift diving just a perfectly normal part of diving? Every trip to Penghu or an overseas drift site is all about enjoying the thrill of the ride — am I overreacting?

What we're describing here is an unplanned drift — one that does not follow the direction defined in the dive briefing. Because the direction is unexpected, you may end up moving in a completely opposite direction, leaving the boat crew with no clear idea of where you are when you surface. You could even be swept into a surge zone, making surface searches significantly harder. In the Editor's admittedly brief diving career, there have been two occasions of being carried away in a direction not defined in the dive briefing.

One happened in the Maldives. The briefing called for a Channel Dive — the Maldives sits on isolated islands in the open ocean, and the channels (Cannels) cutting through the atolls generate powerful currents during tidal changes, attracting large numbers of predatory species. After the dive, we were supposed to be "flushed" by the current into the calmer lagoon waters inside the atoll to wait for the boat.

But that day the current was weak, and we ended up trapped near the island at the channel entrance. We floated on the surface for nearly 30 minutes before the dive boat spotted us. Fortunately, the relatively calm water inside the atoll meant everyone was still laughing and soaking in the Maldives' island scenery.

The second drifting experience, however, was genuinely life-flashing-before-your-eyes territory. We were diving in waters west of Eluanbi, Taiwan. According to the dive plan, we were supposed to drift northward — but after entering the water, a strong current dragged us south. Along the way, we were thrown through exhilarating washing-machine turbulence, and in the surge zone the Editor witnessed, for the first time in Taiwanese waters, a congregation of sharks. That excitement lasted only a few seconds before the powerful current yanked us back to reality.

Most divers know that Eluanbi is one of Taiwan's most notorious current zones. Even on a clear, cloudless day, you can see rolling swells kicking up whitecaps on the surface — and that's exactly where we were taken. It was the first time in my life I felt genuinely afraid while diving.

Three-metre swells swallowed divers between wave peaks, turning each of us into a tiny, invisible black dot on the surface — nearly impossible to spot from a distant vessel. The fierce current rocketed us to positions we could never have predicted, vastly expanding the area any rescue boat would need to search. That scene you've only ever seen in movies — a fishing boat appears in the distance, you shout until your voice gives out, and nobody hears you — when that becomes your reality, you'll be very glad you're holding a rescue beacon.

How to Choose from 4 Rescue Devices

There are 4 types of water-activity rescue devices commonly seen in Taiwan

There are currently 4 types of marine rescue devices commonly seen in Taiwan: the Poseidon System, the Little Dolphin Tracking Locator, the Nautilus Lifeline GPS, and the Garmin inReach. Many people don't know how to choose between them — or worse, they buy one without ever learning the correct way to use it. If an accident does happen, that's a moment of genuine heartbreak. The Editor will walk through each of these four devices with a brief overview. If any experienced seniors are willing to add their insights, please feel free to reach out!

Poseidon System

Unlike the Little Dolphin and Nautilus Lifeline — which use the AIS transmission protocol and will be introduced shortly — the Poseidon System uses LoRa (Low-Power Wide-Area IoT) transmission technology. A receiver is placed on the boat and the diver wears a transmitter; the boat crew can then monitor the diver's movements in real time via a mobile app, even while the diver is underwater.

Update on 2023.3.22 — after the Poseidon System manufacturer contacted the Editor: The Poseidon System also offers a relay station solution, which functions similarly to a land-based AIS station, enabling surface device positioning from shore. The manufacturer has already installed relay stations at the White Lighthouse on Xiaoliuqiu and at Guanshan in Kenting, Pingtung. According to manufacturer data, the coverage range extends from the Qixingyan area to the waters off Kaohsiung. The Editor looks forward to seeing more relay stations installed at elevated points around Taiwan to expand the system's reach.

Supplementary information from the Poseidon System manufacturer: land-based relay stations can be deployed to extend the positioning range

Setup cost: Please refer to the official website.

Advantages: Easy to use — all you need is a receiver and a transmitter. Divers' positions can be checked in real time via a smartphone app.

Disadvantages: It is unrealistic for an individual diver to purchase both the receiver and the transmitter. If the boat operator does not already have this system, additional coordination is required, and someone must be designated to monitor the app onboard.

Best suited for: Water-activity operators looking to build out the system and offer it as a value-added service to clients. Organised dive groups or research teams that can divide responsibilities to deploy the system as a unit.

Little Dolphin Tracking Locator

Developed by veteran dive instructor Piston — a pioneering figure in Taiwan's diving community — based on his many years of hands-on experience in water search and rescue operations, the Little Dolphin is an adapted product built on the AIS transmission protocol. AIS stands for Automatic Identification System: it is an automatic tracking system installed on vessels that, once the device receives positioning information via satellite, shares the vessel's location, heading, speed, and bearing with nearby ships and maritime authorities.

The key feature of the Little Dolphin Tracking Edition is that the moment you surface, the receiver aboard the boat begins tracking your position. You effectively become a small blip on the radar of every vessel and maritime authority in range. The manufacturer also developed a Little Dolphin Rescue Edition, which functions similarly to the Nautilus Lifeline: when you press the distress button, all vessels and land-based AIS stations within effective range receive a rescue signal.

However, AIS has one blind spot: not all foreign vessels are equipped with an AIS receiver — the Philippine outrigger banca boat being a familiar example — or they may use other communication tools. In such cases, the Little Dolphin will have no effect.

AIS transmission range is affected by weather, wave height, and even the curvature of the Earth. At extreme distances, the signal may still fail to get through. Never assume that holding an AIS rescue device means you are 100% safe — always layer your precautions when diving!

Setup cost: NT$3,900

Advantages: Easy to use. With the Tracking Edition, the boat picks up your signal the moment you surface — no need to send a distress call just to be located. Commercial vessels in Taiwan are required by regulation to have AIS installed, so in principle you can use it directly onboard.

Disadvantages: If you use the Tracking Edition, you appear as a small dot on the vessel's navigation display — if you are genuinely swept away, others will not automatically know that an emergency is occurring. Foreign vessels may not have AIS.

Best suited for: Individual divers who purchase the Tracking Edition and coordinate the display identifier with the boat crew before entering the water. Dive shops can equip their dive guides with the device to monitor group surfacing positions.

Nautilus Lifeline GPS

Like the Little Dolphin, the Nautilus Lifeline also transmits via the AIS protocol and enjoys considerable recognition in Taiwan. Multiple divers have been rescued thanks to this device, giving it an impressive real-world track record. (Line Today: The AIS Nautilus — Not a Shell, but a Life-Saving Beacon). However, some users have not operated it correctly — at best resulting in water ingress and device damage, and at worst accidentally triggering a distress alert and wasting national search-and-rescue resources.

Both the Nautilus Lifeline and the Little Dolphin Rescue Edition are intended for genuine emergencies only. Boat crews will typically brief divers beforehand: do not activate the device while the vessel is still within visual range, because the moment you press the button, both the vessel's navigation display and rescue units across the country will receive a distress signal and initiate a search-and-rescue operation. There have been past incidents where a diver activated the Nautilus Lifeline as a test while still on the boat, causing the Coast Guard to mobilise unnecessarily.

Once the Nautilus Lifeline or Little Dolphin Rescue Edition is activated, a distress signal appears on vessel AIS receivers and land-based stations

Once a vessel accepts a rescue mission, the AIS system displays the distressed party's position and the rescue route

Sharing the same AIS protocol as the Little Dolphin, the Nautilus Lifeline faces the identical blind spot: if a foreign vessel has no AIS receiver installed — or uses a different communication system — the Nautilus Lifeline will be ineffective.

Setup cost: NT$6,200 (reference price at Scuba Warehouse official website)

Advantages: Commercial vessels all have AIS, so the barrier to adoption is low and the device is easy to use.

Disadvantages: The housing is prone to water ingress — based on feedback from adopting dive shops, the annual failure rate is approximately 20%. Foreign vessels may not have AIS. Accidental triggering is common, including cases where divers activate the distress function while still within visual range of the boat, causing national rescue units to mobilise.

Best suited for: Individual divers who can activate the distress signal if they are unfortunately swept away.

Bonus Tip: How to Prevent Water Ingress in the Nautilus Lifeline

The Nautilus Lifeline O-ring does not require "activation," but it should still be checked regularly for foreign matter or salt residue — routine cleaning is sufficient
When loosening or tightening the screws, alternate between both sides so the load is distributed evenly across both screws
When tightening the screws, do not force them — tighten only until you feel resistance, then give each screw a small additional turn

Garmin inReach

The Garmin inReach uses the Iridium satellite network — which provides 100% global coverage — to send distress signals via satellite communication. When you press the SOS button outdoors, the signal is transmitted via satellite to Garmin's 24/7 International Emergency Response Coordination Centre (Garmin Response).

The centre will first attempt to contact you using the contact information you have pre-registered, to confirm that you are genuinely in distress. If they cannot reach you, they will simultaneously contact your designated emergency contacts. Once a genuine emergency is confirmed, they will immediately notify the local search-and-rescue authority for the location from which the signal was sent.

According to a Garmin engineer, on one occasion they accidentally pressed the SOS button — and received a call from Garmin Response within approximately 5 minutes.

The Garmin Response search-and-rescue procedure

Beyond SOS signalling with truly global satellite coverage, the Garmin inReach also allows you to send text messages. You can pre-set a library of template messages, or send key information directly to your contacts. According to the most recent dive-related rescue incident report from Garmin Response, in late May 2022 a dive vessel in waters off the Galápagos struck a reef. Before the vessel sank, the distressed party managed to locate a Garmin inReach and activate it. Throughout the ordeal, they exchanged messages back and forth with emergency services, sharing critical information such as the number of people needing rescue and the location of a potentially safe area nearby.

During the drift, the person also remained in constant contact with their spouse in Florida, USA. Reflecting on the experience afterwards, they said:

"If I hadn't been able to communicate with my wife that night, it would have been a terrifying ordeal. It was truly priceless."

Every product has its strengths and limitations, however. The Garmin inReach carries a higher upfront cost compared to the other options, and because satellite service requires separate registration and a subscription contract, that is an additional ongoing expense. That said, divers tend to use relatively few messaging credits, so based on the rates currently listed on the official website, the standard individual SAFETY plan should be more than sufficient.

Additionally, Taiwan's satellite regulations are relatively strict — there is currently no sufficiently accommodating legal framework to allow companies to offer the device as a rental service. Each unit must be registered under an individual's name, and this will require the NCC (National Communications Commission) to consider relaxing the relevant rules in order to promote wider adoption.

The Garmin inReach must be configured in advance to access the full range of rescue services

Setup cost: NT$12,990 (Chunghwa Telecom listed price)

Advantages: Compact device. Works globally (excluding North Korea, China, India, Russia, Iran, Thailand, Vietnam, and a few others). Active distress signalling increases the probability of a successful rescue. Two-way messaging allows you to share critical rescue information and reassure your family.

Disadvantages: Higher upfront cost; requires a monthly subscription fee. Currently not available through Taiwanese dive retail channels — must be purchased through Chunghwa Telecom or the Garmin official website.

Best suited for: Divers planning dives at higher-risk sites, divers who frequently travel overseas, and divers who want the most proactive rescue capability available.

Conclusion

Getting home safely is the one thing no water-activity participant should ever compromise on

This article has introduced four of the most common marine rescue devices available in Taiwan. Each product has its own characteristics, and users should fully understand those characteristics before purchasing and using one — otherwise, you've spent the money but the device may fail to deliver its most critical function when you need it most. That would truly be a waste.

There is one more essential point to never forget: throughout this article, the emphasis has consistently been placed on the word surface. No matter which rescue device you use, you must first surface before you have any chance of sending a distress signal. So when an accident occurs, stay calm at the surface, take out your rescue device, and use it correctly as instructed. Safe diving, everyone!

The recommendations below reflect the Editor's personal diving habits and modest experience — they are offered as a general guide. Experienced seniors are warmly invited to share their own insights.

If you are a boat operator: The Poseidon System, Little Dolphin, and Nautilus Lifeline are all suitable, but should be used according to the specific situation. If the vessel already has AIS, the Little Dolphin and Nautilus Lifeline can be adopted directly.
If you are a casual recreational diver: The Nautilus Lifeline and Little Dolphin Rescue Edition are great choices — just make sure to stay close to your dive guide, and in the event of an emergency, use the device correctly.
If you are an intermediate diver: Use the Little Dolphin Tracking Edition together with the Nautilus Lifeline. On the surface, the Tracking Edition lets the boat crew see you; activating the Nautilus Lifeline lets the rescue team see you.
If you are an avid, experienced diver: Take any of the above options and add a Garmin inReach to enable active distress signalling — so you can explore remote dive sites around the world with complete peace of mind.

One last reminder worth repeating: "Maintaining your safety equipment matters — don't skimp on O-rings and battery replacements."

海編"布魯陳"

我是布魯陳，平常喜歡帶著大相機下海找生物，如果你有海洋議題歡迎找我聊聊，約我吃飯更歡迎！