Do you Plan your dive or Dive your plan within NDLs?

[Basking Ridge Diver]

How do you pre-plan a multilevel dive or do you? Do you plan the dive using a manual approach (table or other method) or do you use a paid subscription software application?

Does your pre-plan include your expected RMV, gas volume and time requirements to stay within the NDLs? Or do you jump in and monitor on the fly your dive based on your SPG (AI) and PDC?

It can be a boat or shore dive - I am interested in your approach to a pre-plan or lack of pre-plan.
Thanks in advance.

 

[tbone1004]

depends on the dive.

If I'm going in a quarry or some other mostly confined area, I just fly by the computer because I'll never get close. If I'm doing ocean diving I'll preplan somewhat. I know my SAC rate *don't use RMV, it's the wrong term, SAC is the right term*, and I know the tank size, and I know the bottom. So I do rock bottom calculations and then work back from what is left and that is my bottom time limit. That combined with the mix will give me a nitrogen intake level and allow me to plan decompression. I use Pastodeco because it's easy and cheap and allows me to input gradient factors, but if you are diving with a computer it is crucial to use plan based around their algorithm.

I don't bother with NDL's because I am deco certified, so if I rack up a 5-10 minute mandatory deco on backgas, it isn't the end of the world, I'd rather use the gas at the bottom then limit myself with an NDL

 

[lowviz]

I always head straight to the deepest part of my dive first. Never been bent, rashed, or otherwise compromised. No reverse profiles.

I'll play with both GAP and V-Planner the night before a deeper dive to get a feel for downtime. Yes, I fly my PDC but I also know what it should be telling me. I keep a slate on my wrist with "terminal dives" on air. Square profile dives. Tells me how long I can stay at a given depth, come up with stops, and have gas to spare but not share.

Buddy diving is a whole different animal. I use the IANTD SAC rationing approach.

 

[tursiops]

Do you plan the dive using a manual approach (table or other method) or do you use a paid subscription software application?

There are other alternatives: some computers allow you to plan a multilevel dive, including SAC/gas usage, and there is plenty of free software you can use. Like tbone, what I use depends on the dive, the dive buddies, and whether I've done that particular dive (or ones like it) before.

 

[Storker]

I hardly ever dive square profiles, I prefer multilevel to maximize bottom time. Since I'm usually required to give my planned max run time and max depth to the boat tender/dive leader, I have to have a decent idea of the limits of my dive even before I splash.

I've got a few "standard" multilevel - or rather two-level - profiles which I've simulated on my PC and use as a basis for most of my dives. I also have a small two-column table on my slate, listing a some three or four depth/min pressure combos which all are calculated using my SAC and the min gas principle for buddy divers. Those are my limits, but I often do more conservative dives. As long as my actual depth/time combo is within the limits of my pre-planned dives, I can be pretty sure that I'm fine.

In addition I naturally monitor my computer's remaining nitrogen time and my gas consumption during the dive. Reality beats theory every time

 

[mattia_v]

I generally start a dive deep and move up as I go - although 'deep' is generally less than 30m, usually more like 25, and move up 10 to 15 over the course of the dive. I'm strictly recreational single tank, usually nitrox, and the timer on the computer very rarely goes below 30 minutes, and pops back to >100 by the time the dice ends. On Bonaire (most of my diving to date) my mandatory surface interval was generally between nothing and 1 minutes.

 

[t-mac]

Depends on the dive and where it is in the day's sequence. If it is shallow and at the beginning of the day, I don't really do anything. I usually get cold (or risk being last on the boat) before either air or NDL could be a problem. Of course, I monitor both during the dive anyway. After the first dive, I check my NDL on my computer at my planned maximum depth (square profile planning) and a little deeper and always dive the deepest part of the dive first and work my way up (like mattia_v). If I'm doing multiple deep dives in a day, I pay a lot closer attention, but I always have a good idea of how long I can stay at depth before I splash and then I adapt based on the computer to budget my time. I have a pretty low SAC and so air is not usually limiting except during deeper dives that occur early in the day's sequence and so my planning really is mostly based around NDL.

 

[TMHeimer]

Most of my shore dives are irrelevant as they are never much deeper than 30. I rarely take a charter, so I have to be extra diligent. I plan with tables, but also use the DC. Most are square profiles. I don't plan anything specific for the second boat dive, as site plans can change. But after dive No.1 I re-check tables to see my NDL for #2--then I also follow the allowable bottom time on DC. I use watch & depth gauge as well.

 

[Kharon]

Almost never dive a square profile. On Bonaire I go straight out to as deep as I'm going, turn left or right, slowly swim up the slope at a shallow angle to at or near safety stop depths , turn back and return along the edge of the reef.

 

[Patoux01]

If NDL diving, I don't really care about the plan. I'll just find a turn pressure and that's about it. No max time for me (no boat, no wife, no whatever).

I do have something of a plan in terms of directions however... Just so my buddy and I agree on where we go and what we do.