Review: Halcyon Symbios Handset Dive Computer

As part of its new Symbios lineup, Halcyon Dive Systems has released its first-ever dive computer: the Halcyon Symbios Handset. Known for their high-quality dive gear, Halcyon entering the computer market raised some expectations—and I was eager to see if the Symbios lived up to the brand’s reputation.

Thanks to Fjords Underwater Explorers, I had the opportunity to borrow a unit for long-term testing. Over several weeks, I’ve dived with it in cold water conditions, both fresh and saltwater, and here are my detailed impressions.

Build & Form Factor

The Symbios Handset is impressively built—sleek, durable, and extremely low-profile. Compared to other high-end units like the Garmin Descent X50i and the Shearwater Perdix 2, it is significantly lighter and slimmer, which improves comfort and reduces snag risk underwater. 

💡 Display

The 2.4-inch display with 320x240 resolution is bright, high contrast, and easily readable even in direct sunlight. I used it on maximum brightness during all dives to stress-test the battery, but in most cases, it could easily have been dimmed without sacrificing readability. Overall, the screen performance holds its own against any computer in its class.

Battery Life

The handset features a non-user-replaceable rechargeable battery—a design choice that has both pros and cons. While I’ve often relied on the ability to swap AA lithium batteries in my Shearwater units to rescue a dive, having a built-in rechargeable battery removes the hassle of carrying spares.

Despite its compact form factor, battery life exceeded expectations. Even with full brightness and gas integration enabled, the unit handled multiple long cold-water dives without issue. The manual states a runtime of up to 30 hours, and based on my experience, this is a realistic figure.

Usability & Interface

The interface is logical, intuitive, and responsive. Once familiar with the menu structure, I found it more user-friendly than Shearwater’s—though switching from a system I’ve used for years (Petrel 3 on JJ-CCR) did require some mental adjustment. I tested the Symbios both as a standalone unit and in tandem with my Shearwater, and despite the initial challenge of managing two systems, the Symbios performed well.

Dive Modes

I tested all available modes except closed-circuit with wireless pO₂ integration (which requires a Symbios ECCR or a compatible oxygensensor). The unit performed flawlessly in open circuit, bottom timer, and fixed setpoint CCR mode. Resetting average depth and accessing the stopwatch were simple and quick—two features I find particularly helpful in bottom timer mode.

Decompression Algorithm

The Symbios supports Bühlmann ZH-L16C with configurable gradient factors, the gold standard in most tech diving today. You can adjust the gradient factors freely, which is crucial for tailoring the decompression model to your specific needs, without going into the debate on whats the «correct» GFs. It’s rated to 120 meters, and comes with an onboard compass and vibration alerts—features expected in this class.

Air Integration & Trim Sensor

While I’m personally skeptical of wireless tank transmitters, especially from a training perspective, the Symbios transmitter works well. The unit supports up to 9 transmitters and includes a trim and tilt sensor. Surprisingly, I found the trim feedback to be genuinely useful—though a well-trained buddy can offer the same information, having a constant reference on screen was informative and encouraged better awareness.

 The Companion App

The app is clean, intuitive, and feature-rich, offering easy customization and logbook integration. It’s also a strong foundation for future firmware upgrades. I didn’t test the social community features, but for device management and dive logging, the app worked flawlessly.

Minor Drawbacks

The biggest issue I encountered was the button size. In thick dry gloves, the buttons are difficult to press without concentration and deliberate effort. Wrist angle adjustments helped somewhat, but I’d love to see slightly larger or more glove-friendly buttons in future iterations.

Final Thoughts

The Halcyon Symbios Handset is a strong debut in a competitive market. It combines excellent build quality, a beautiful display, and a smart interface into a lightweight, low-profile package.

Its key strength lies in simplicity and refinement—and while the lack of a user-replaceable battery might deter some divers, the performance speaks for itself. I haven't tested the Symbios HUD yet, but it looks promising as a complement to the handset.

Pricing in Norway has yet to be confirmed, but I expect it to fall in line with other high-end computers. If you're in the market for a streamlined, high-performance dive computer, the Symbios deserves serious consideration.