Logging dive time vs bottom time

[meatsim]

It's your dive logbook you can do as told above - as you like. Or, for now, you can follow standard training protocol and follow the above instructions from the RDP instructions. Again, your call.

i understand the difference between the two, looking at my bottom time is just something i don't normally do or remember if i do and it is easy to pull the time from the computer at a later time.

The sites i dive tend to have some vertical profile to them so the times i have gone back and checked the PG and NDL limit from the table based on the bottom time the computer let me do i have always been well outside of the limits so i cant see it being a back up in case my computer fail (as in to transition to tables for future dives, if a computer fails on a dive that dive is over). I don't have any experience manually calculating multi level dives


but i'm getting off topic, i've just wondered why my PADI logbook only had room for bottom time not dive time or both when the majority of diving in off computers these days, might just be the case that not much thought goes into it

 

[TMHeimer]

Agree of course. You follow the tables (computer...) and PADI (or whatever agency) rules as to what constitutes bottom time, and plan your dive(s) that way. You also can just add in the ascent and safety stop time if you have a watch and desire to. As long as you're safe and happy....

 

[Neilwood]

Fairly new Padi OW diver here and all I log is the overall dive time straight from the dive computer. Hard to do otherwise atm as I am still using rented gear so can't see a full dive profile. My dives have all been shore dives with a drop to about 6m, swim a square (going to about 10-18m) and then surface at the buoy so bottom time is relatively irrelevant (the entire dive is "bottom time"- just at varying depths of bottom!).

Depends on what you are using to plan your dives I reckon. If using the computer, use total time. If using ERDPML, use bottom time.

 

[Bob DBF]

Assuming things not in evidence - I assume you went through PADI training, recently. This is what you should have studied in your first classes regarding using the RDP.

The Recreational Dive Planner comes in two different forms, the Table version and The Wheel. Regardless of which version you use, there are several general rules you must follow. Apply the following rules anytime you use either version of the Recreational Dive Planner. 1. Bottom time is the total time in minutes from the beginning of descent until the beginning of final ascent to the surface or safety stop.

It's your dive logbook you can do as told above - as you like. Or, for now, you can follow standard training protocol and follow the above instructions from the RDP instructions. Again, your call.

When I was using tables it was described as ...your direct ascent to the surface, which would mean leaving the bottom and ascending to the surface at the specified ascent rate. On a 60' dive, if you followed the bottom up at less than the specified ascent rate, or went up to 30' and looked at the reef for a while, it would count as part of your 60' dive until you made your direct ascent to the surface. Because of this multilevel dive planning was born, but didn't last long because the dive computer came along and is easier, faster and more accurate.



Bob

 

[Neilwood]

When I was using tables it was described as ...your direct ascent to the surface, which would mean leaving the bottom and ascending to the surface at the specified ascent rate. On a 60' dive, if you followed the bottom up at less than the specified ascent rate, or went up to 30' and looked at the reef for a while, it would count as part of your 60' dive until you made your direct ascent to the surface. Because of this multilevel dive planning was born, but didn't last long because the dive computer came along and is easier, faster and more accurate.



Bob

That approach really punishes shore dives (taking the pattern of one of my dives last weekend as an example) as you descend at the buoy at 6m, swim a square pattern with the first leg being a gradual descent (following the bottom) to your ultimate depth @ approx 18m, swim parallel to the shore for a period, then swim an upward leg again following the bottom back to 6m, and then swim back to the buoy parallel to the shore at 6m. So you have been offgassing for a large period of the dive which tables give you no credit for.

I think I will stick with a computer!

 

[glassbottom]

I have always just logged the dive time as displayed by the computer, my instructor filled out the first few dives and that is all they did so i just copied them. On a shallow dive there probably isn't too much difference however I normally do slow ascents, from 130ft with a safety stop there would probably be a 10 min difference between bottom time and the dive time the computer registers.

My OW instructor told us to log the time in the water (from the moment you start descending) to the moment you surface - the safety stop and ascent from your deepest depth. IE: if the dive was 35 minutes on a profile of 60 fsw you use 30 minutes BT, subtracting 2 minutes for the ascent and 3 minutes for the stop).

That said, he re-iterated that if you wanted to run tables using the TOTAL time (ie: 35 minutes) that was fine too it just may change your group letter and allow you less dive time overall, but this was fine as it was just more conservative.

I use a slate+watch to record my essential data and use the above method.

 

[NAM001]

For what my opinion is worth is would call dive time being time in water.

i understand the difference between the two, looking at my bottom time is just something i don't normally do or remember if i do and it is easy to pull the time from the computer at a later time.

The sites i dive tend to have some vertical profile to them so the times i have gone back and checked the PG and NDL limit from the table based on the bottom time the computer let me do i have always been well outside of the limits so i cant see it being a back up in case my computer fail (as in to transition to tables for future dives, if a computer fails on a dive that dive is over). I don't have any experience manually calculating multi level dives


but i'm getting off topic, i've just wondered why my PADI logbook only had room for bottom time not dive time or both when the majority of diving in off computers these days, might just be the case that not much thought goes into it

---------- Post added October 5th, 2015 at 04:30 PM ----------

You make a good point. That point is the center of all non tech debate with computers and tables. Every thing has assumptions and some tables are square profile assumptions. because of this there are different assumptions to each manufacture of tables. gather several tables and read them. you will see the differences if you look. some use only physiucal bottom time with no up and down, others use decent time as being on the bottom. (adds a margin of safety).

That approach really punishes shore dives (taking the pattern of one of my dives last weekend as an example) as you descend at the buoy at 6m, swim a square pattern with the first leg being a gradual descent (following the bottom) to your ultimate depth @ approx 18m, swim parallel to the shore for a period, then swim an upward leg again following the bottom back to 6m, and then swim back to the buoy parallel to the shore at 6m. So you have been offgassing for a large period of the dive which tables give you no credit for.

I think I will stick with a computer!

 

[bowlofpetunias]

Most of our dives are shore dives and bottom time is the same as dive time. We go in and follow the contours down.. when we reach the turn point we follow the contours back up again to the exit. We are off gassing as we slowly ascend during the dive. Our final ascent would take seconds rather than minutes in many of our sites we have gotten so shallow we just stand up climb the rocks out or walk out.

I was taught to log the entire dive. If the dive isn't 20 minutes it is not logged as a dive for the dive count but the details are recorded for reference. It was drummed into my head that any time you are breathing compressed gas under pressure should be recorded. If you take a hit or feel unwell that information may be important for Dan or the medical professionals treating you. If someone needs to know I can tell them my safety stop time otherwise it is all the same to me.

 

[archer1960]

I just log total dive time (my computer says it starts counting when it gets 3 ft deep). I never have a safety stop on a shore dive, because we start swimming in about 5' of water, and swim back in until we can stand up again. So my "safety stop" is the return leg of the overall swim, and it's always way more than 3 min. Often we only spend a few minutes deeper than 15' anyway, because of the shallow slope of the bottom profile.

 

[bowlofpetunias]

yes that is often the case with us too.... lol sometimes the entire dive is about the safety stop depth