When it comes to scuba diving, much attention is often lavished on the descent and the bottom phase, where exploration, enjoyment, and sometimes technical challenges abound. Yet, ironically, the ascent - arguably the most critical phase of any dive - is frequently overlooked or treated with casual disregard. This neglect can have serious consequences, not least the risk of decompression sickness (DCS), commonly known as "the bends," which can occur if divers ascend too quickly or neglect their stops.
The ascent is far more than a simple return to the surface. It is a carefully orchestrated, highly technical process that demands concentration, teamwork, and a thorough understanding of physiological principles. It is no exaggeration to say that every dive, regardless of depth or duration, is a decompression dive - every stop is a decompression stop. Understanding and respecting this fact is paramount to safe diving.
At the heart of ascent safety is the management of inert gas absorbed by your body tissues during the dive. As you breathe compressed air (or other breathing gases), nitrogen dissolves into your bloodstream and tissues. The deeper and longer you dive, the more nitrogen is absorbed. If you ascend too rapidly, this dissolved nitrogen can come out of solution too quickly, forming dangerous bubbles that cause DCS.
The critical takeaway is that no dive is “no-decompression” in an absolute sense. Every ascent must be controlled to allow your body to safely off-gas this inert nitrogen. Hence, the much-misunderstood "safety stop" is not a mere formality but a vital component of decompression management - and it should be thought of as a bona fide decompression stop.
Safe ascents are rarely solo endeavours in technical or even recreational diving contexts. Instead, the ascent is a coordinated team exercise with distinct roles and responsibilities. The team dynamic ensures that tasks are shared, situational awareness is maximised, and errors are minimised.
- Dive Leader: Signals the start of the ascent, sets the pace, and ensures clear communication among team members.
- DSMB Handler: Deploys and manages the delayed surface marker buoy (DSMB), monitors depth closely, and manages the reel line.
- Timekeeper: Watches the stopwatch or dive computer to monitor stop durations and ascent timing.
- Other Team Members: Maintain formation, monitor surroundings, support emergency interventions if necessary.
Assigning these roles before the dive and reinforcing them during the dive significantly reduces the cognitive load on any one diver and enhances the overall safety margin.
A DSMB is an essential piece of equipment for every dive. It serves not only as a safety device signalling your position to boats and shore personnel but also as a practical tool for depth management during the ascent.
Why deploy a DSMB?
- It alerts surface vessels to your location, reducing the risk of collision.
- It aids in managing your ascent speed and depth by providing a physical reference point.
- It offers a line to maintain team formation and coordination.
When to deploy?
Generally, it’s advised to deploy the DSMB from around 10 metres depth or shallower. Deploying from too deep can introduce complications such as entanglement or excess drag, which may disrupt your ascent control.
Just as the descent requires deliberate positioning, the ascent demands precise team formation and diver trim.
- Two-person team: Face each other, approximately two comfortable fin kicks apart, maintaining visual contact and communication.
- Three-person team: Form a star shape with clear sightlines between each diver, ensuring situational awareness and ease of communication.
Maintaining horizontal trim throughout the ascent is critical. Ascending vertically is a common but dangerous mistake: it hampers efficient off-gassing and makes managing emergencies much harder. Horizontal trim facilitates better control, energy efficiency, and readiness to react swiftly if something goes awry.
Effective communication underwater is more than rote signalling. It requires active cognitive engagement with the information being exchanged.
- When the dive leader signals a manoeuvre or instruction, every team member must process the meaning, confirm understanding, and only then respond with the agreed signal.
- Avoid mechanical or automatic repetition of signals without comprehension, which can lead to confusion and errors.
- Clear, deliberate communication underpins a smooth, safe ascent.
The ascent speed must be slow and steady. The dive leader sets the pace, ensuring no rapid gains in depth. Meanwhile, the DSMB handler carefully monitors depth, managing the reel to keep the buoy vertical and the line taut.
The DSMB line should never be slack, as this allows the buoy to drift and undermines team position. The reel should be locked intermittently by clipping the boltsnap to the spool, securing the line while allowing controlled pay-out.
A typical ascent involves multiple decompression stops, each at a preplanned depth for a prescribed duration. For example, the first stop might be at 6 metres for one minute, followed by a stop at 3 metres for another minute.
Timing options include:
- Starting your timer as you begin the ascent and including travel time between stops in the overall stop duration.
- Starting timing only once the target stop depth is reached for a more cautious approach.
Modern dive computers typically have integrated stopwatch functions, making this straightforward. Alternatively, some teams record video of the ascent with a running timer visible for a reliable time reference, and to review later for debrief and improvement.
While it may feel instinctive to hold the reel tightly or thread fingers through the spool, this is a hazardous practice. In case the buoy catches a passing boat, a tightly held reel can drag a diver underwater.
Safety measures include:
- Never inserting fingers through the spool’s centre.
- Not clipping the reel to your gear.
- Being prepared to release the reel immediately if the buoy is caught.
- If the reel sinks, the line remains accessible for recovery once on the surface.
A useful and often overlooked tip is to use your DSMB line to gauge surface wave conditions during stops. By locking the reel and holding the buoy in front of you, the fluctuations in line tension and buoy depth provide an immediate visual cue about wave activity, allowing you to prepare for a safe and controlled final ascent.
While decompression stops might seem dull, they can be productive if used wisely. Practising previously mastered skills during stops can maintain alertness and improve proficiency-provided these activities are preplanned and don’t interfere with safety priorities.
Before surfacing, the team must thoroughly check the surface environment for hazards such as boats or other divers. Each diver should cover the area above other team members, confirming that it is safe to proceed.
The final ascent from the last stop to the surface should be the slowest part of the dive. The pressure gradient near the surface is steepest here, and a slower ascent reduces the risk of DCS significantly.
Aim to surface directly beneath the DSMB, maintaining team cohesion until completely clear of the water.
It remains a common misconception among divers that ascending vertically is proper or easier. This position compromises off-gassing, reduces control, and hampers emergency responses.
Instead, adopting and maintaining horizontal trim is safer and more efficient. To see the surface while maintaining trim, divers can gently tilt their heads up or, if needed, invert briefly for a clear view, even when carrying heavy steel twinsets or sidemount gear.
Operating your DSMB and ascent procedures with precision-attention to spool management, line tension, hand positioning, and team roles-is essential. For example, opening the double ender boltsnap with your thumb and locking the spool by hooking it through one of its holes prevents line slack and buoy drift.
The ascent may seem like a simple return to the surface, but it demands the same discipline, teamwork, and focus as every other phase of a dive. Mastering this phase not only protects you from decompression sickness but elevates your diving to a professional level of safety and confidence.
