Have you found yourself at a dive site watching CCR divers prepare for a dive and wondered what it would be like to join them? Perhaps some of your dive buddies have recently gone over to (more) silent, bubble-free diving, and you wonder if you can still join them? Or maybe you’re the one CCR diver in your group of friends and not to sure how to integrate everyone else. No matter which of those circumstances describes you best, this blog is for you.
What is Mixed Team Diving?
Let me start at the beginning: the idea for this blog was born in April. When I read the programme for Rebreather Forum 4, I stumbled across a presentation on ‘Mixed Team and Mixed Mode Diving’ by Mauritius Bell. Knowing that diving in Truk Lagoon in December would almost certainly involve some of that, I made sure to attend the session. You don’t need to have heard it to follow this blog, but if you’re keen, you can watch it here.
Mauritius Bell’s background is mostly in scientific diving, where he has led expeditions involving rebreather divers, open circuit divers, surface-supplied divers and sometimes even breath-hold divers. Within the context of scientific diving operations, there is a distinction between mixed mode and mixed platform diving.
Mixed mode diving refers to the combination of different types of diving, such as open circuit and closed circuit diving. Mixed platform diving then refers to divers using different rebreathers within the same team. For the purposes of this blog, I’ll stick to the term mixed team diving and clarify the context.
Mixed Team Diving With Dark Horizon Diving
What I couldn’t have foreseen when I attended the presentation was just how much mixed team diving we would end up doing this year in Gozo and Malta. Those dives included combining twinset, Sidemount and CCR in one team as well as conducting dives with team members on different rebreathers. Whether these are guided technical dives or fun dives with friends, they require extra attention.
Even if you’re not a CCR diver (yet), you may know that rebreather diving qualifications are unit-specific. Just because you can dive one CCR doesn’t mean you’re allowed to dive all of them. Training and certifications are structured like that because of significant differences between rebreathers. Preparing for that type of dive means learning enough about your teammates’ rebreather to recognise when something may be wrong and offer a degree of assistance.
The differences become even more noticeable when you’re mixing open circuit and closed circuit divers in the same team. Different rebreathers may work differently, but the basic principles remain the same. That’s no longer the case when OC and CC divers enter the water together, so it’s safe to say the dives require more preparation.
Key Considerations for Mixed Team Diving
So, where do you start when you’re getting ready to mix different dive modes or platforms? Here are three key considerations for mixed team diving:
- Understanding equipment differences
- Dive planning and decompression considerations
- Dive briefing and logistics
1. Understanding Equipment Differences
It’s almost too obvious, but I’ll say it still: CCR divers can’t expect their OC buddies to magically understand how a rebreather works. That means they need to set aside enough time to introduce buddies to the basics. Check out this blog by Tim Bloemeke for DAN Europe for a great summary on what that includes. Incidentally, Tim’s blog was inspired by the same Rebreather Forum presentation.
Just as importantly, OC buddies should never be afraid to ask their CCR-diving friends if something is unclear. That’s often easier said than done and puts us into the territory of human factors in diving. I won’t follow that tangent for the moment, but I want to make the point that there is a degree of responsibility on both sides.
In practice, understanding your teammate’s equipment better means asking questions. Here are a few examples of questions a great teammate could ask:
- What are the most common problems you could experience?
- Is there something I should look out for as your teammate? (Flashing red indicators on CCR computers are a tell-tale sign of a problem, for example.)
- How can you help me in case I run out of bottom or deco gas?
Don’t wait until it’s time to jump off the boat to discuss those differences. The evening before a dive is a good time to discuss them. Alternatively, consider meeting early enough on the diving day to cover equipment differences without needing to rush.
Differences Between Rebreathers
The same principles apply to dives that bring together different rebreather brands in the same team. Depending on the type of CCR, differences may be small. However, when you start combining manual and electronic rebreathers (mCCR and eCCR), the differences get bigger and it’s critical to talk about them.
Generally speaking, descents and ascents are the busiest times for rebreather divers. This applies even more to mCCR divers who don’t have a solenoid that injects oxygen to maintain a certain partial pressure of oxygen (PPO2). mCCRs rely on the diver to maintain their PPO2, which requires extra focus on ascents.
Someone who has always dived eCCR and perhaps never really considered mCCRs may not necessarily be aware of those differences. Setting aside time for a thorough introduction is essential to prevent problems as much as possible.
2. Dive Planning and Decompression Considerations
Assuming their rebreather is working correctly, CCR divers have almost unlimited gas supplies. They need to consider the limitations of their CO2 absorbent and their bailout gas, but in most cases, the OC diver will determine the duration of the dive.
The CCR diver in the team needs to understand and accept what the limits of the OC buddy are. When you agree to team up with someone in a different equipment configuration, you have to be happy to stay within their limits, even if that means shortening your own dive.
If you’re planning a decompression dive, there are a few more aspects to consider. For a start, decompression stops may vary somewhat between the OC and the CCR diver. In addition, OC divers will almost always have to plan for gas switches. CCR divers need to be aware of when and where those switches occur and support their teammates.
What kind of support could you give? It could be as little as confirming the switch is safe. If there is a problem, though, CCR divers may need to donate (one of) their bailout gas(es) to their OC buddies. In fact, it’s a good idea to practice gas donation regularly, especially in a mixed team.
3. Dive Briefing and Logistics
By now, you’ll probably realise that mixing teams requires some degree of extra effort. Is it worth it? Yes, because it gives OC divers an excellent insight into how CCRs work on real dives. Plus, it forces divers to think about their team diving practices in greater depth. As a result, divers will find their knowledge of equipment expanding, and that’s a good thing!
In practice, aligning mixed teams translates into dedicating additional time before the dive. To be clear, the dive briefing just before you splash is not the right time to address all the differences we mentioned above. Planning successful mixed team dives starts earlier to ensure that no one is forced to rush through the process.
Mixed team briefings should cover:
- Differences between individual CCR units
- Differences in gas and decompression planning and how they’ll be accommodated
- Potential problems and emergency procedures
Depending on the scope of the dive or project, you’ll find yourself adding to this list. Accordingly, your ‘pre-project’ talk or dive briefing will have to be adjusted, too. It all comes back to dedicating an appropriate amount of time.
There’s No Rush!
Speaking of rushing, have you noticed that CCR divers generally take a bit more time to get ready? There are a few reasons for that: setting up a rebreather takes longer than putting together open circuit scuba equipment. With greater experience, the preparation requires less time, and experienced CCR divers generally have no problem to enter the water on time.
How do they do that? It’s not magic. The more hours you accumulate on your rebreather, the better you understand how long it takes to get ready. As the OC buddy, you may notice that your teammate is starting to prepare earlier than you are. That’s normal, no need to be alarmed.
At the same time, when you’re changing tanks or getting a refill between dives, your CCR buddy may well have very little to do. All that depends on the details of your dive(s), though.
Final Thoughts
Should you dive in mixed teams? With the right preparation and with everyone’s goals aligned, mixed team diving can be hugely rewarding and deepen divers’ knowledge of different types of diving. To be successful, mixed team dives rely on thorough preparation.
Last but not least, remember one of the golden rules of technical diving: any diver can call any dive for any reason at any time without fear of repercussion. So, if someone suggests a mixed team dive that you’re unsure about, ask all the questions you need in order to understand exactly what is expected of you, and if you’re not comfortable, sit this one out.