SEA Explorers Club

In the next few weeks Davy Jones’ Tech are planning a trip to Song Hong sinkhole in the south of Thailand. Led by head Technical Instructor David, we are planning a Trimix dive to 100m in the sink hole, accompanied by 3 other divers who are Trimix and Full Cave certified. Song Hong lake is the gateway to a huge underground river, which is believed to flow all the way to the sea which is over 60km away, where it flows to and from is unknown due to its depth and sheer size. The deepest dive made in the cave was 140m and over a kilometer in, and this barley scratches the surface. The purpose of this trip is to try to explore more parts of the cave and have some fun at the same time! The roof of the cave starts at 40m and wen you are on the main line you cannot see the bottom or any other walls, despite the water being crystal clear below 30m. It is a great dive, especially if you are interested in cave diving and the possibilities exploration that it offers.

If you are new to Technical diving, or looking at getting into it, then there is a word that you would have heard getting thrown around quite a lot. Trimix, and if you have already started your technical diving career then you probably have some basic understanding of what it is, but may be unsure of why it is used, and it’s advantages and disadvantages.

To put it basically Trimix is a breathing gas with 3 main gasses in it, Nitrogen and Oxygen (standard breathing air) and Helium. Trimix comes in endless different blends, all of which have their own use in technical diving. The main reason Trimix is used is to extend your depth. Using air the deepest that you can go is around 60M (however most training agencies say 50m or 55m). This is because as you go deeper the partial pressure of Oxygen gets too high and it would be unsafe to go any deeper. So to go deeper we must get rid of some of the Oxygen from the breathing gas, and this is where Helium comes into the mix. Once we start to add some Helium the percentage of the other gasses begin dropping and now we can start to go down further. This is the main advantage of Trimix, it allows us to go to places where we cannot go using air, and however there is one other major advantage. As you are probably aware of, when we start to go deeper than around 30m we begin to feel the effects of ‘Gas Narcosis’ kicking in. Helium however is non-narcotic so when we start to add the Helium we reduce those narcotic effects, which is great if you are doing anything that is more complicated than just swimming around a wreck i.e. penetration or complicated navigation. So some training agencies will start to use it for going deeper than 30m, so narcosis doesn’t even become an issue. There are however some disadvantages to Trimix, the main one is the price, Helium is not a cheap gas, and this is why rebreathers are becoming more and more popular, as you can use trimix in a rebreather and because your body doesn’t use the helium it just gets recycled, and this cave save considerable amounts of money!

If you are interested in extending your bottom depth then we can teach PADI Trimix 65 and Full Trimix (which maximum depth is 90m) or TDI Advanced trimix (which maximum depth is 100m). It is great training even is depth isn’t your thing, as you will learn to deal with many problems all at once (with the surface not being an option)

As a technical diver you need to have a back up of everything, So we are going to talk about dive computers today. So again, as this equipment is a very important part of your kit, you need to have have at least 2 of them. The problem with dive computers is that even different models from the same brand, they can come up with very different decompression information, especially as you start to head deeper and spend longer underwater. Now another problem with them for technical diving, is that they assume that you spend the entire dive using the same gas. However as Tec divers we can switch onto different gasses to either speed up (accelerate) our decompression stops or to make them more conservative. There are a few dive computers that allow you to switch gas as you make your way up to the surface, however again these computers all use different models and can have great differences from one model to the next. One feature many computers have, is called ‘Gauge Mode’. This mode allows you to turn of all nitrogen tracking information so all you have is depth and time (which gets rid of a very annoying beep beep beep that happens when you get near or hit a limit). But most dive computers are only rated to about 100m, which may seem deep but once you get the bug you will want to go deeper and deeper! So what can we do? Enter UWTEC with their depth gauge timers. These devices are wrist mounted, accurate electronic depth gauges which have a clock/timer included, These gauges are rated to a depth of 330m (which just happens to be as deep as anyone has gone using SCUBA) but as they are NOT a dive computer (no nitrogen tracking) they are comparatively cheap, infact you can pick 2 of them up for less than the price of a watch style dive computer, and even for recreational diving, once you get to know the tables well enough then there is no reason why you can’t use these devices solely.

We are running another Tech Deep instructor program here at Davy Jones Tech, this time we have got long term DJL instructor Tom, who has also been doing lots of Tech diving here over the past year. And also Scott who has been teaching on Koh Tao for many years, but recently discovered Tech diving and now he can’t get enough of it! The instructor course is an intensive internship that has several different practical and theory sessions. One of the parts that they have to complete is a skill circuit where they have to demonstrate skills perfectly and then watch a student complete the skill to a level of mastery. They must also give lectures on things such as the history decompression theory, where they need to have an in depth understanding of everything that they are going to be teaching, as people who are interested in Technical diving are always keen to ask questions to further understand the type of diving that they are going to be doing. Overall the course takes a few weeks and by the end of it they will be teaching actual Tec 40, 45 and 50 students (while under supervision from one of our tech instructors) and then a final exam must be completed. It is a great course to take if you would like to make technical diving a part of your career, not to mention that it looks good to have on any diving CV, especially as Technical diving is ever becoming more and more popular.

More often than not when we go Technical diving we will end up having to make decompression stops, as a result of staying at depth for so long. These decompression stops vary in lengh, as a tech 40 diver you can make 10 mintues of “deco stops” however as you get more advanced you can make longer and longer dives which means more deco time. Now it is not always possible to come back to your ascent line. This means that you have to make a “hang deco” which means no line, just mid water. If there is a current running it is very easy to get carrier quite a distance if you have a lot of deco to do. Which is why it is very very important to have some surface markers and signalling devices. As a stanard you should have 2 seperate DSMBs or Liftbags. SMBs are prefered as they stick higher out of the water and don’t create much drag. One of these should be orange or red, and this is your standard one, and the other, Yellow which is used for emergancies only. As well as this you should carry an audible device such as a whisle. Many technical divers in areas with strong currents actually carry somthing called a “drift kit” which has various items in the event they get caught in a current and  need to signal the boat. This might include a mirror, a phone, flares or even an EPIRB (electronic position indictating radio beacon). As a bre minimum you need 2 DSMBs/Liftbags and a whistle. There are many options available, however ideally they fold up into a small bundle, easy to inflate and are easy for boats to see. There are even some that we have here for sale at Davy Jones Tech that only take one breath to fill up, and then once they are up they self seal and s