minimum surface time for shallow depths

[HJ]

Hello All,

I've read the DCS threads on the Safety forum (a bit scary!), I've studied the nitrogen loading table from Trux (cannot find the AIDA tables on their site), and all of this is a bit bewildering to a semi-beginner about to go on a dolphin-swimming/fun freediving Bahamas trip next month.

Assuming max depths of 10m, slow ascent rates (<1m/sec), I seem to be coming up with a minimum surface time of 4 mins. For someone who is interacting with dolphins and wanting to spend as much time underwater as possible (with no plans to exceed 1 min per dive and probably no more than 10-20 dives per day), 4 or even 5 mins feels like an eternity. Are there other opinions or resources that can lead me to feel comfortable spending less time on the surface between relatively shallow dives?

Opinions appreciated. -- HJ

[cdavis]

You are unnecessarily concerned. In those depths and/or the conditions you describe, DCS is not a problem for freedivers. Its just possible in twice that depth but requires long bottom times and a whole bunch of dives.

Surface interval? For 1 minute dives in 10 meters, 2 minutes should be fine, but that depends a lot on you. A little longer will make you safer and probably more comfortable, especially for longer dives.

Sounds like a great trip; have fun.

Connor

[Fondueset]

I agree. If your dives are long - over 2 minutes - you will start to get a headache if you don't breathe up sufficiently. I try for a 3 to 1 ratio but when its cold or there are a lot of boats around it is difficult to sustain.

[cdavis]

Thought about this a little more.

Your challenge, when you get into dolphins, will be maintaining sufficient surface interval to support the max possible bottom time. 30 seconds is going to seem like 10 eternities with a couple of dolphin right below you. If you go back down too quick, like 1 minute or less , you will not have restored your 02 or C02 mechanisms even though you may feel ready to dive. Makes for the next dive being not relaxed, too short and uncomfortable. You will be very tempted to hyperventilate, get your C02 down quickly and go. That doesn't work and too much of it can put you in BO territory (not real likely for a semi-beginner, but worth considering). Before you get into dolphins, experiment with dives that look like what you expect to do with them plus different surface intervals. Everybody is different, but you will probably find that a surface interval slightly over 2 minutes will get you the most bottom time. You may find that dives of longer that 1 minute are quite possible if you relax (no small trick with dolphins around) and extend the interval. A 3 to 1 ratio works pretty well for longer dives in that kind of depth.

Good Luck and bring us a report when you get back

Connor

[azapa]

hj, I am very new at this, and quite square too. Here is my take though.

I use a Sunnto dive watch, the d3 or mosquito. They will measure your dive time, and on arriving on the surface, automatically start to count that surface time, whilst still displaying your recent dive time in the bottom right. Sorry if it sounds confusing, but just look for relaxing at least 2x the past dive time. Even after 5 dives it will become very easy and natural to do.

If dives exceed 15m, or you feel that the 2x is still not enough, maybe because you are exited, cold, tired, current, your body should tell you by the crappy dives. In this case back off to 4x or even more. YMMV.

If you listen really hard to your body, you will start to know when you are ready again, which is quite a bit after you initially feel ready. You will see beginners doing 1x dive/surface, because the think they are good to go. It may take 6 months of diving to be able to listen carefully enough to really know though

we demand a full trip report + photos!

[Fondueset]

The single biggest thing that has really helped my bottom times is deep relaxation during the surface interval. Focus on that and breath naturally - just let your body go and relax deeply - then try to keep that through the dive. Eric Fattah advocates remaining absolutely motionless during surface intervals and the effect is amazing.

[HJ]

Hey, great input! I just came back from pool and the 2:1 interval seemed about right (1 min dive, 2 mins surface). But this was in a pool and without real depth (3m). I need to keep practicing to see how it feels. Also good points about relaxation.

I'm getting excited now! And will have my UW digital camera so you guys will be getting the full report with -- hopefully -- some pix and/or video. Of course, I've got to get someone to take pictures of me. I'm usually never in the pictures 'cause I'm taking them!

HJ