Minimum Gas…Play it Safe!

By , 3 November, 2015, No Comment

When planning deep dives, wreck penetrations, as every responsible diver knows, there should always be a reason; the old adage of “plan your dive, dive your plan” springs to mind.


Emergency planning is a key part of diving; everyone on their Open Water learns the Alternate Air Source or good old CESAAAAA, but what happens when you are too deep for a CESA? Your buddy better be on hand to help you, but even then will you have enough gas to make it out safely? Let’s look at an example to highlight just how much air might be needed for you and your buddy to make a safe ascent:


First of all we need to make some assumptions. The first one is that with all the “panic” of your buddy’s gas loss (total failure) then you both will be breathing a lot faster, so we are going to say 30L/min. Then it will take you both a couple of minutes to get sorted before you make your ascent. Now let’s look at the maths:


  1. Out of Air!=


Two of you breathing from a single tank at 30L/per min at 40m:

= 5 (depth in bar) x 30 (L/min) x 2 (people) x 2 (minutes) = 600L


  1. Ascent


Ascending up to 5 m from 40 m at 12m/min breathing from a single tank

= 2.8 (avg. depth in bar) x 30 (L/Min)x 2 (people) x 3 (minutes) = 504L


  1. Safety Stop (Three Minutes at Five Metres)

= 1.5 (depth in bar) x 30 (L/min) x 2 (people) x 4 (minutes including ascent) = 270L



= 600L + 504L + 270L = 1,374L

= 124 bar (11L tank)


This means that to be on the safe side, you should be ascending up from 40m with at least 124 bar in your tank in case of emergency in order for both divers to make it out safely.


This is just one of many Gas Planning calculations that can be done in order to carry out a safe dive. Whilst alot of this is only covered in ‘Technical’ diving, the same principles still apply in any sort of diving.


So come and do a PADI Deep Specialty with me, and start learning more about the Underwater World!

by Chris








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Plonger à Davy Jones Locker Koh Tao

By , 22 October, 2015, No Comment

De Rescue Diver à Idc Staff Instructor

Bonjour à tous, je m’appelle Jean-Philippe (J-P).

Je vais vous parler de mon parcours et de comment je me suis retrouvé à Djl Koh Tao. J’ai quitté Montréal en 2013 pour venir en Asie pour quatre mois, c’est à ce moment que j’ai découvert la plongée sur Koh Tao, j’ai fait un dsd (discover scuba diving) et j’ai su dès que j’ai sauté à l’eau que c’était ce que je voulais faire comme travail, instructeur! J’ai continué mon voyage et sur la route j’ai fait mon Padi open water course ainsi que mon Padi advanced open water course :) le monde sous marin est vite devenu une passion! J’ai ensuite plongé au Vietnam et j’ai changé de plan je suis allé en Australie, ou j’ai aussi fait de la plongée, plutôt que de rentrer à la maison! Après 1 an et 7 mois en Australie je suis revenu à Koh Tao pour 1 mois pour faire de la plongée et mon Padi rescue diver course, sur recommendation d’une amie en Australie, à Djl. Ça fait maintenant 10 mois… (J’ai, depuis cessé de faire des plans ;)!). Après mon rescue diver course comme l’ambiance et l’équipe à Davy Jones Locker me plaisait bien je suis resté et j’ai commencé mon programme Padi Divemaster pour entrer dans le monde de la plongée professionnelle. Le programme Divemaster fut une formidable expérience ou vraiment on se forge une expérience au sein d’un groupe de plusieurs jeunes dynamiques qui sont là pour la même raison, on en apprends beaucoup plus sur la plongée pendant toute la durée du programme et on fait la fête, que de plaisir ! En quête de défi, j’ai ensuite bien réfléchi et j’ai décidé de devenir instructeur pour avoir la chance de partager et transmettre ma passion, s’en est suivi le Master scuba diver trainer et le Padi Idc Staff Instructor pour pouvoir formé tant de nouveaux plongeurs que de futurs instructeur. Voilà où j’en suis aujourd’hui, après 10 mois sur Koh Tao, je vis sur une des plus belles îles du monde et fais l’un des plus beau métier du monde, merci DJL de m’avoir acceuilli dans la famille.

Que de joie venez me voir et on s’en parle :)

Ou alors envoyer moi un email a si vous avez quelques questions que ce soit.

Au Plaisir!!










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By , 17 October, 2015, No Comment

Barracuda, large and stealth like, one of our oceans most stealthy predators. Recently i have been lucky enough to encounter a great barracuda up close and personal. Barracudas are elongated fish with powerful jaws. The lower jaw of the large mouth juts out beyond the upper.
Barracudas possess strong, fang-like teeth that are unequal in size and set in sockets in the jaws and on the roof of the mouth. Barracudas are elongated fish with powerful jaws. The lower jaw of the large mouth juts out beyond the upper. Barracudas possess strong, fang-like teeth that are unequal in size and set in sockets in the jaws and on the roof of the mouth. The head is quite large and is pointed and pike-like in appearance. The gill covers do not have spines and are covered with small scales. The two dorsal fins are widely separated, with the first having five spines and the second having one spine and 9 soft rays. The second dorsal fin equals the anal fin in size and is situated more or less above it. The lateral line is prominent and extends straight from head to tail. The spinous dorsal fin is situated above the pelvis. The hind end of the caudal fin is forked or concave, and it is set at the end of a stout peduncle. The pectoral fins are placed low down on the sides. The barracuda has a large swim bladder.
The great barracuda that i encountered recently at the Wreck was roughly 5ft long and you could see the power in its large body, it seemed perfectly at ease around us divers and was swimming around us contentedly. It came extremely close to us during the dive but not in a threatening way at all, more like it was showing off. It is known that barracuda have a tendency to be attracted to shiny objects, somewhat like magpies, they mistake the shine for prey. Although they seem rather menacing up close there has been very few human attacks and those that have occurred have been due to mistaken identity.
It was wonderful to see such a powerful underwater creature as close as i was lucky to get, yet another reason to get under the surface and see these fish up close.


by Dani



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Bucear en Koh Tao

By , 25 September, 2015, No Comment

Bucear en Koh Tao es una de las experiencias mas bonitas que puedes hacer en tu vida. La libertad y la ingravidez que nos proporciona el estar bajo el mar son sensaciones incomparables.
A parte de las sensaciones generadas, también podemos disfrutar de la incomparable vida marina que tenemos en la isla.

Con Davy Jones Locker centro PADI ***** podrás visitar los diferentes sitios de buceo que hay en isla tortuga. Inmersiones semanales en Chumpon, Southwest, Shark Island …  entre otras, harán que disfrutes como nunca del fondo submarino.

Algunos de los animales que puedes encontrar y “sentir” en Koh Tao, son estos curiosos Labroides Dimidiatus , conocidos oficialmente como “Cleaner Fish”

Estos pequeños se han especializado en limpiar parásitos y tejidos muertos a los peces del arrecife.

Este pequeño comilón es un amigo muy querido por todos los habitantes del mar, ya que vive agrupado en colonias en las que permanentemente se acercan peces de todas las especies y tamaños para que los libre de los parásitos, de los cuales se alimenta. Actualmente podemos encontrar muchos de ellos, especialmente en sitios como White Rock, Mango Bay, etc. Estos granujas ya han aprendido que los humanos también tenemos pieles muertas y parásitos, así que no dudan a la hora de limpiarte tus heridas y pellejitos. Son totalmente inofensivos y muy divertidos!










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Considerations for ‘How Much Gas’

By , 21 September, 2015, No Comment

“1/3 in, 1/3 out and a 3rd in reserve”, “surface with a third of all your gas”, “save a third of your gas for emergencies” are typical statements you may hear when talking about rule of thirds.
The rule of thirds is variously attributed to either the pioneers of cave diving in the UK and the founders of what was to become the Cave Diving Group (CDG) or to their slightly more modern counterparts exploring the springs of North Central Florida.

Regardless of origin, the rule was used by cave divers, allowing one third of the gas supply to be used on the inward journey, one third for the dive out and a third held in reserve in case things did not go according to plan.

In simple terms it seems to work.  Looked at more closely there are flaws, albeit only minor, which need to be addressed as part of your dive plan in order to stay safe if things go wrong.

First let us look at the common belief that we should dive ‘to’ the rule of thirds.  For this example we will assume identical breathing rates and identical cylinder sizes between two dive buddies.  Should one diver have a catastrophic loss of gas at the furthest point of penetration the other diver has a third of his gas ready to donate to the out of air diver.  However if the process of the first diver trying to deal with the gas lost in the first instance takes any time or the act of sharing air and sorting themselves out for the exit takes more time, the diver donating gas will have been using some of his or her exit gas already.  Those few minutes to get organised for the swim out could leave gas supplies perilously close to the limit or even being exhausted prior to the team reaching safety.

What if the air sharing swim out of the cave takes much longer just because the long hose has been deployed?  What if the two divers did not have identical breathing rates?  If the out of air diver has a measurably larger breathing rate then the donor diver’s reserve third might simply not be enough gas!

How can we plan to avoid these potential pitfalls?

Firstly we can look at how we might apply the rule of thirds before we discuss other planning considerations.  When I said that many divers will dive to the rule of thirds the implication is that they will turn the dive when the hit the point of having used 1/3 of their gas.  But turning around takes time.  Making sure everyone on the team has seen the signal and they too have turned takes time.  All this is eating in to the gas for the swim out and as so in to your reserves as well.

Perhaps now would be a good time to have a look at how we go about calculating our turn pressure based on the rule of thirds.

Let’s say we have a starting pressure of 210 bar.  That one is nice and easy, 210 divided by 3 is 70 bar, so each third is 70 bar.  70 bar from our start pressure would mean the turn pressure is 140 bar.

What if the stat pressure is not a nice easy number to divide by 3?  I know a few divers who can seemingly instantly divide almost any starting pressure by 3 and calculate their turn pressure.  I have also seen diver then use this very precise pressure during the dive when they have digital readings or pressure.  However I have also noticed how this seems to entice those divers to go right to the limit of their gas.

Simpler and safer would be to err on the side of caution and make the maths easier.  Just for fun I will look at a couple of examples.

A starting pressure of 220 bar is not easy to divide by three in your head whilst bouncing around on choppy seas discussing the dive plan and turn pressures.  Far easier is to round the number down to the next lowest number that is easily divisible by 3.  In this case that would be 210 bar.  The usual turn pressure for 210 bar would be 140 bar (210 – 70) but in this case we are starting with 10 bar more, so very simply, calculate how big 1/3 is from our rounded down pressure (70 bar here) and subtract that from your actual starting pressure. 220 bar – 70 bar would give a turn pressure of 150 bar.  70 bar in and 70 bar out would leave the ‘largest 1/3’ as the reserve, 80 bar.

What about 200 bar start pressure.  Well 195 bar is easily divisible by 3.  Each 1/3 would be 65 bar.  65 bar subtracted from your actual start pressure would give a turn pressure of 135 bar.

For some that calculation might not be so easy but there is no reason why you can’t write a list of start pressures and turn pressures in your wet-notes so you don’t have to worry that your maths isn’t so good or that you might get it wrong.

When you have calculated or looked up your turn pressure don’t just tell the team what your turn pressure is, tell them how much gas you have and then what your turn pressure will be.  That way you get a few other brains to check that you have got it right.  After all, it is their safety too that could be jeopardised if someone gets it all wrong.

Remember too that for wreck penetration dives, while still using the same approach with the rule of thirds, it is applied a little differently.  We have to take in to account the fact that having exited the wreck, in most cases, we still have an ascent to make and possibly decompression too.


At Davy Jones Tech all this information and more is covered during training, so you fully understand and you can put it into practice.


Contact us now if you want to further develop and expand your diving.

by Matt



Twin set

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