Safety-critical rebreather software

With a time-sensitive contract and a firm deadline, JFD needed a trusted team that could step in, take ownership, and deliver—without compromising on safety.

JFD Global, part of James Fisher & Sons Group, is a leading underwater capability provider, serving the commercial and defence markets with innovative diving, submarine rescue and hyperbaric technical solutions and services. Its systems are designed for use in complex, safety-critical subsea environments where reliability is essential.

In such environments, system reliability is essential. Even minor software defects can pose an unacceptable risk to user safety—and mission success.

From review to rebuild

The Stealth Multi-Role SMR® is JFD’s most advanced rebreather: a compact, software-driven system designed for user comfort, safety, and endurance during extended underwater operations.

JFD invited Bluefruit Software to bid on the software development scope of work. The two companies had previously worked together on a successful precursor project. That prior collaboration gave JFD confidence that Bluefruit could offer a safe and reliable solution.

Bluefruit scoped the full embedded software development in C++, building continuous integration, validation, and regular stakeholder visibility into the delivery plan. JFD’s response was decisive: Bluefruit was entrusted with full responsibility for the rebreather’s embedded software.

Taking ownership

Bluefruit committed to a rigorous delivery schedule:

Timeline: Deliver the required embedded software in nine months.
Scale: Deploy four dedicated teams comprising 24 full-time engineers.
Scope: Provide firmware, software, integration, and hardware support.

Using a Lean-Agile approach, Bluefruit delivered working “vertical slices” of functionality every two weeks. This enabled early testing on target hardware and reduced reliance on late-stage integration. Regular demos kept stakeholders informed throughout.

The team built core system elements in C++ to ensure a production-ready foundation. Functional safety requirements were also embedded into day-to-day engineering practices, ensuring that compliance and quality were baked into the development process, not bolted on at the end.

Project highlights at-a-glance

Alpha (14 weeks)

10 weeks to working system on target hardware
Closed-loop oxygen control achieved from scratch
78 user stories, 129 system requirements, 42 functions

Beta (22 weeks)

Multi-sensor hardware integration (analogue and digital PO₂)
PC application and diver alert system delivered

MVP (44 weeks)

Full safety-critical feature set implemented
Decompression, calibration, and dive analysis capabilities
Integrated with Revision 4 hardware

A proven system, ready for iteration

JFD received the agreed embedded software deliverables on schedule and in line with the revised, evolving plan. Delivery included EN 14143 compliance—the European standard for closed-circuit self-contained diving apparatus.

The clearest measure of success came shortly after delivery: the JFD team performed a successful manned dive using its next-generation rebreather and the newly developed embedded software. This marked a critical milestone: a real-world validation of the system’s safety and reliability.

With a robust and maintainable software foundation in place, JFD has been able to take SMR to market with confidence. It is also future proof; new features can be added quickly, tested rigorously, and validated to support ongoing enhancement.

"The immense effort shown by Bluefruit led us to safely and successfully completing our first manned dive with the new embedded system. The passion and commitment shown by the entire team has been fantastic."

- Steven Coull, Head of Technical Sales, JFD Global

What Bluefruit provided JFD

Accelerated delivery: A focused, full-time engineering team brought structure and momentum to a complex project
Continuous validation: Regular delivery of working software allowed for ongoing testing and reduced integration risk
A robust foundation: A safety-aligned C++ codebase is ready for iterative development and new features
Confidence in product: The software was successfully validated through a manned dive