True Blue Dive

True Blue Dive True Blue Dive Training Centre is your link for fun learning & discovering & exploring the best dive sites in NSW, Australia. What do we do best?

You can set your limit…from total relaxed up to full adrenaline! Teaching diving

Through CMAS, we offer all types of dives and training, accommodating people from all different backgrounds. The World Confederation CMAS was established in September 1958 and by now it comprises over 130 national federations from 5 continents. In addition to organizing international underwater sport events - through

its respective committees and commissions and through its member federations - it is at the forefront of technical and scientific research and development. It can be associated with the oldest and most extensive dive-training systems. All our courses are ruled under TrueBlueDive™ Training Standards, exceeding all minimum international standards. Our company ethos is to provide a safe, detailed and practical application of Scuba training, where safety and quality are held in higher regardless the certifications we offer. We have elected to work through CMAS, as it was the original international diver training standard, focusing on dive research and equal opportunities for all. We call it: “Working with the Best”

As a CMAS representative, and as part of Cousteau’s Dive Team, we will ensure that by the end of each course, every student will become a competent and safe international scuba diver, becoming part of Cousteau’s Dive Team with an international certification, recognized anywhere in the world, for the rest of their life! We call it: “Training Guaranteed”

We operate most dive sites between both New South Wales Marine National Parks: Port Stephens and Jervis Bay. Our DiveHeadquarters® is located on the Central Coast due to our diversity of dive operations, spanning five different locations (Newcastle, Central Coast, Northern Beaches, Eastern Suburbs and South Coast), to allow you to dive closer to your home. Your advantage as a TrueBlueDive™ customer is that we plan and provide our services according to the location preference of the customer. We call it: “Mobile Operation”

Courses are not conducted according to a set calendar. You can choose take the course in a row or in different dates and in one or in different locations. We call it: “Flexible Calendar”

Within your chosen location, we always pick the best dive site according to the weather and water conditions for a given day. All components of our dive courses are conducted on site, including dives, practical training and diving theory. You can register, choose, book or change your preferred date and location available for your dive/course in our 24/7 self-service on-line Booking System. We call it: “Freedom”

TrueBlueDive.com was designed to offer you a great opportunity to experience the true blue sense of scuba diving as well as discover and explore down under, from a different and unique point of view. All the programs and activities are specially designed and fully guaranteed with the support in most languages, for those with zero of experience up to the ones with a lot. For our teaching and training we choose to work with CMAS (Confédération Mondiale des Activités Subaquatique), the first international agency training in the world, which has a worldwide respect and recognition that guarantees you serious fun and serious diving. However we do recognize other international certification agencies, when you enrol or book with us for dives or advanced courses (such as AUSI, IDD, NAUI, PADI, PDIC, SDI, SSI, TDI). We call it: “Friendly Program”

We also conduct special programs through the CMAS Scientific Commitee such as: Oceanology & Marine Science and Wrecks & Underwater Archeology. All the services organized and provided by DiveHeadquarters® and offered through TrueBlueDive.com are almost unique in the industry, with high quality and fully experienced professional instructors, uncompromising in its training standards and customer service. We invite you to visit and dive in our site, to explore our TrueBlueDive™ services & activities. Click below to check our packages:

- Open Water Diver Course
- Advanced Open Water Diver Course
- Specialties Courses
- Dives & Tours
- Corporate Packages

Even if you’re not a certified diver you’re more than welcome to enroll in our snorkeling packages or our challenging Introductory Dive specially designed for people with no experience whatsoever. If you are a certified diver and you have a “friend” diving with us, we will be more than happy to invite you to our Dive Buddy offer where you can come along on the day and dive with your friend while he is taking the course.

13/08/2018
08/06/2017
30/03/2017

Decompression Theory: Half Times Explained

The history of decompression theory. This was the work of Paul Bert and John Scott Haldane as well as Robert Workman and Prof Albert Buhlmann.
The information on half times and tissue compartments, one of the key concepts in decompression theory.

Half Times Explained

Half times are a common concept in science. The most famous use of half times is in relation to nuclear materials where the half time is the time it takes a radioactive substance to decay to half of its current size. This is exactly the same concept applied to the uptake of Nitrogen by a tissue compartment. The half time of a compartment is the time it takes for the compartment to become half saturated, or if we are ascending to become half desaturated.
So if we consider a compartment with a half time of 5 minutes this means that compartment will become 50% saturated within 5 minutes. It will then take a further 5 minutes for the compartment to move from the current state to half way to saturation, i.e. 75%. The table below shows the progression of the tissue saturation at 5 minute intervals.

5 min 50%
10 min 75%
15 min 87.5%
20 min 93.75
25 min 96.88%
30 min 98.44%
We can see from this that the largest movement takes place during the first half time period, each subsequent half time period then sees a smaller and smaller change. If we draw a graph of gas uptake over time we can see a smooth line that initially shoots up but then gets ever shallower as it reached 100%.

Half time graph

Mathematically the tissue will never reach 100% as it only moved half of the way from where it is towards 100% at each stage so it takes smaller and smaller steps towards it’s goal but always has the other half of the last step to cover. However, for practical purposes, after 6 periods we can consider the tissue saturated as it is at 98.44% saturation and after 24 hours we would consider the tissue to be completely saturated.

Each compartment will saturate at a different rate. As we have seen after 5 minutes the 5 min tissue is 50% saturated but the 10 min tissue will take 10 minutes to become 50% saturated and so on. This means that each of the tissues will have a different level of saturation with the fast tissues absorbing gas and moving towards saturation faster than the slow tissues. However, as the diver ascends and the pressure is reduced the fast tissues will also release inert gas faster as the half time also refers to the time it takes to release 50% of the absorbed gasses. This means that fast tissues will also release gases faster then slow tissues.

tissue compartment half times

From the graph above we can see the behaviour of a number of compartments when considered together. As we have seen above the 5 min compartment is 50% saturated after 5 minutes, at 10 minutes it is 75 % saturated and so on until 30 minutes or 6 half-time periods it is effectively saturated (98.44%). The 10 min compartment is 50% saturated after 10 minutes. After 40 minutes the compartment is not yet saturated as this has only been 4 half time periods. It would require 6 half-time periods (60 minutes) for this compartment to become effectively saturated. The 40 min compartment is at 50% saturation at 40 minutes but all of the slower compartments; 80, 120, 160 and 200 min, are less then 50% saturated.

At 40 minutes the pressure is released and the compartments start to desaturate. The 5 min compartment was the most saturated but as it desaturates equally fast the level of saturation quickly drops to below that of the 10 min compartment and soon drops below the other compartments until at time 60 minutes, 20 minutes after the pressure was released, the 5 min compartment is less saturated than all of the other compartments. The 10 min compartment also drops quickly so that at 48 mins it drops below that of the 20 min compartment.

16/12/2016
22/08/2015

The Index is a comprehensive scientific measure of the ocean’s overall condition. It advances ocean policy, compares future progress, and informs decisions regarding marine ecosystems worldwide.

Back soon
17/09/2014

Back soon

Very handy...sometimes.
23/10/2013

Very handy...sometimes.

25/08/2013
Although shark attacks can seem vicious and brutal, it's important to remember that sharks aren't evil creatures constan...
10/08/2013

Although shark attacks can seem vicious and brutal, it's important to remember that sharks aren't evil creatures constantly on the lookout for humans to attack. They are animals obeying their instincts, like all other animals. As predators at the top of the ocean food chain, sharks are designed to hunt and eat large amounts of meat. A shark's diet consists of other sea creatures -- mainly fish, sea turtles, whales and sea lions and seals. Humans are not on the menu. In fact, humans don't provide enough high-fat meat for sharks, which need a lot of energy to power their large, muscular bodies.
If sharks aren't interested in eating humans, why do they attack us? The first clue comes in the pattern that most shark attacks take. In the majority of recorded attacks, the shark bites the victim, hangs on for a few seconds (possibly dragging the victim through the water or under the surface), and then lets go. It is very rare for a shark to make repeated attacks and actually feed on a human victim. The shark is simply mistaking a human for something it usually eats. Once the shark gets a taste, it realizes that this isn't its usual food, and it lets go.
The shark's confusion is easier to understand once we start to look at things from the shark's point of view. Many attack victims are surfers or people riding boogie boards. A shark swimming below sees a roughly oval shape with arms and legs dangling off, paddling along. This bears a close resemblance to a sea lion (the main prey of great white sharks) or a sea turtle (a common food for tiger sharks).

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