This is the third video in my three-part series on Halcyon’s Symbios dive computer system, and today I’m looking at the Halcyon app—the bit of software that really ties the handset, HUD, and tank pod together. If we’re being honest, most scuba manufacturer apps suck. This is the first one I’ve used that feels genuinely all‑encompassing, and it’s clearly been built around the reality that everyone already has a phone in their pocket at the dive site. Out of the water, the app becomes your main controller: pair your Symbios devices, scroll through settings, program gases, and then hit sync to push everything over via Bluetooth. I had a flawless experience doing exactly that, and the preset feature is a massive time saver if you dive similar profiles or mixes regularly. Beyond setup, the app acts as a detailed logbook, includes a social logbook (with an active community), lets you save digital cert cards, register products by serial number, contact customer service, and even run a simulated dive profile in the “Learn” tab—something I can absolutely see being useful in a classroom. Stepping back, what’s interesting is how Symbios is designed to grow with you: from a new single-cylinder diver with air integration, all the way through tech, teaching/filming with the HUD, and eventually CCR integration. Dive safe, dive often.