A Comprehensive Guide to Technical Dive Planning / Part 1

Let's face it, every dive is actually planned. Even simply agreeing with a friend that you're going diving at Swan Lake and meeting at 5:00, is a plan. What is crucial, however, is the level of detail, sophistication and care that goes into preparing the dive. This will vary with the difficulty of the dive and the various conditions that come into play. Putting two extreme examples against each other, the level will be dramatically different for a routine recreational dive versus a challenging technical expedition to an unexplored site in a remote area. Contrast a few minutes of deliberation between two friends versus a year's preparation by a multi-person team. Let's focus on the plan for a technical scuba dive without the support of a dive center, which often solves many things for us.

So let's go through the different elements that each plan should contain. If possible, all team members should prepare the plan together or at least consult with each other. If only one, usually the most experienced team member or event leader, is preparing the plan, he or she should thoroughly brief the other team members on the plan during a joint briefing. Team members must then demonstrate that they are familiar with the plan, understand it and understand their role and assigned tasks.

Location and weather
Sometimes the choice of the place is clear and we plan everything else around that, and other times we put together criteria of what we would like to see, experience, discover and what we have available. If we choose a place in the latter way, we have to turn to literature, maps or specialised websites with a database of sites. The location of wrecks can be guessed by local fishermen who repeatedly lose their nets in the same place. They also have an idea where marine life is concentrated. Local people such as herders, farmers or foresters, who know the area intimately, can help find new caves. Places that are still hidden from our community but that locals have knowledge of, are still plentiful even in today's modern world.

Nautical charts can give us a rough idea of what the bottom relief looks like. Today we can find some online, such as Navionics ChartViewer.

If we have information about a site from a source such as a list of dive sites, a description from someone who has dived there before us, and so on, we can then extract as much information as possible on things such as depth, location, prominent features and landmarks, access to the site, and possible hazards.
The weather can be tricky and can make the event very difficult or even impossible. We need to have long-term and detailed short-term local forecasts. The long term is mainly concerned with choosing the right time of year to hold the event. We can easily find out the average temperature and precipitation in each period, periodic precipitation and winds, tidal forces, currents. In short, to choose the most suitable time of the year for the planned diving. Local short-term forecasting has been greatly facilitated by weather apps and websites such as Yr.no or Windy.com.

Especially the latter can display a huge amount of detailed data about the current weather situation anywhere in the world and forecasts for 9 days ahead, which includes wind, precipitation, waves, currents, tides, sea temperature (at the surface) and more. We have to take into account that there is no perfect forecast. We can consider a forecast up to a maximum of 24 hours ahead as relatively reliable data, while we consider data up to three days ahead as a probable course. Anything beyond the three-day horizon can only be accepted as a rough guide.

The exception is the tide forecast. There, on the other hand, iron-clad regularity and predictability apply. It is, however, very strictly location-specific, and so we must obtain tide tables as close as possible to the location of the planned dive. Timing the dive so that the tidal currents are as small as possible and flow in the right direction during the dive is essential. This is done at the peak of the tide.

Logistics
Logistics is usually the least attractive part of the planning and the event itself. We have to take into account all conceivable operations necessary to carry out the event. Especially how to get to the site, how to get all the equipment there, where to stay, where to rent a boat, where and how to fill the bottles, and so on. The logistics of the dive itself then include deploying the progress or decompression cylinders, providing a decompression ladder, ascent rope and such.

Teams
The basic prerequisite for forming a technical scuba diving team is ensuring sufficient skills, experience and qualifications of all members. Events of a technical nature are often announced with a certain minimum level/qualification required. Where practical teams are divided into support and exploratory teams. Cave diving especially in Europe often requires an extra large team of porters. These do not even have to be divers themselves but must be proficient cavers and climbers. All equipment must be carried through miles of passageways, rarely upright and often by crawling, climbing, rappelling and traversing. This determines the ratio of porters per diver. On a recent historic crossing of a 7 km section in the Moravian Karst, there were 40 dry support team members to two cave divers.
The underwater support team is responsible for deploying the progression cylinders and transporting all the necessary materials and technical diving equipment to the right places and removing those no longer needed. This allows the exploration team to concentrate on reaching the target or making new discoveries.

Choice of technical diving equipment
We use the information about the location and difficulty of the dive to choose the equipment we will need. It would be nice if we could always use the same equipment for all types of dives, but that is simply not possible, despite the beliefs of some fundamentalists. Or at least not yet.
We must first determine the basic equipment configuration. Will it be open circuit or closed circuit? Backmount or sidemount? Dry suit or wet suit? You say to yourself, if I have all that available, why should I choose in the meantime, I'll take the better one, but that certainly doesn't have to be the case. While rebreathers may seem to do all the work, for conditions such as a challenging cave transport to cross a siphon, lightweight self-contained steel cylinders are probably more appropriate. For deep dives closed circuit. For dives with long underwater penetration of a cave or wreck or extreme depths many progression or decompression cylinders, a double rebreather or bailout rebreather are suitable, for narrow spaces a sidemount rebreather. The amount of cylinders and gases then follows from gas management planning, which we discuss below.
For the basic configuration of technical equipment we have to think about what additional equipment we will use. Guide lines, buoys, reels, spare lights, spare cutters, heating systems, scooters, transport bags and boxes, and other technical diving gear.
Some missions require very specific tools and pieces of equipment designed for specific purposes. Biologists like Sonia Rowley or Richard Pyle need trap nets, sampling vials. Other times divers need mapping plates, but also hammers, crowbars, saws, metal detectors, markers, dyes, and so on.

Dive objectives
Ha, this is probably the most fun and adventurous part of the planning. We're discussing with our friends what exactly we're going to do underwater and how the dive will work. We have a map of the site, cave or wreck in front of us and we think about how best to execute the dive. Everyone is assigned their tasks and responsibilities within the team. A timing plan of specific steps to take while on the bottom is made. The exposure will then be determined from that. That is, the depth and time of the dive. These are the necessary inputs for planning decompression, gas management, gas selection and setpoints. But we will talk about that in the next part of this article. We will show the actual calculations and the dive planner app.

Author: Jakub Šimánek