The eRDPml & Multilevel Dive Planning
The electronic multilevel planner is where dive planning gets genuinely useful — and where a lot of divemaster candidates lose points. The logic is simple once you see what it's crediting.
Square profiles vs multilevel dives
The paper RDP table plans a square profile: it assumes you drop to your deepest depth and stay there for the whole dive. But most real dives are multilevel — you start deep and work shallower. Because you on-gas nitrogen far more slowly at shallower depths, a plan that credits those shallower levels can safely give you more total bottom time than the square-profile table allows. That crediting is exactly what the eRDPml does.
What the eRDPml is
The eRDPml — electronic Recreational Dive Planner, multilevel — is a software planning tool that takes a dive described as a series of depth-and-time segments and works out the pressure groups and limits for each, keeping the whole profile within no-decompression limits. Think of it as doing in advance what a dive computer does in real time.
The rules that matter
Multilevel planning only stays safe if you follow its structure, and the exam tests exactly these points:
- Plan the deepest level first, then each subsequent level shallower — never return deeper within the plan.
- Observe the minimum depth change and minimum time at each level the tool requires.
- Carry the ending pressure group from each level into the next, just like repetitive-dive planning.
- Round conservatively — depth and time up — exactly as with the RDP table.
eRDPml vs a dive computer
They apply the same idea from opposite directions. The eRDPml lets you plan a multilevel dive before you get in the water; a dive computer follows your actual profile as it happens. Understanding the planner makes a computer's readouts intuitive — and it's the tool you'll be expected to teach and reason about as a professional.
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Frequently asked questions
What is the eRDPml?
The electronic Recreational Dive Planner, multilevel — a software tool for planning multilevel no-decompression dives. You enter a series of depth-and-time levels and it calculates the pressure groups and limits, crediting the shallower portions of the dive.
Why does multilevel planning give more bottom time?
Because you on-gas nitrogen much more slowly at shallower depths. The square-profile RDP table assumes you spend the whole dive at your deepest point, while the eRDPml credits the time you spend shallower, so it can safely allow more total bottom time.
What order do you plan eRDPml levels in?
Deepest level first, then each level progressively shallower. You never plan to return to a deeper level within the same dive, and you carry each level's ending pressure group into the next.
Is the eRDPml the same as a dive computer?
They use the same multilevel idea but at different times. The eRDPml plans a multilevel dive in advance; a dive computer tracks your actual depth profile in real time during the dive. Learning the planner makes computer readouts much easier to interpret.