Buoyancy Basics Part 2- Salt vs Fresh Water

Scuba Divers in Seawater

Continuing on from our first buoyancy basics blog last week, we will move on to the difference between buoyancy in salt water compared to fresh water. If you haven't read last week's basics, please do, as it underpins what will be read here.

During our scuba diving beginner courses, we learn that if we dive in Fresh water, we need to use less lead weight on a set diving equipment rig than we would in salt water. Generally speaking, if we move from the salty sea to a swimming pool, we drop around 2kgs off our weight belts.

But why is this?

The answer is actually quite complex but we will look at it in the most simple terms possible.  Again, it relates back to Archimedes Principle.

Salt water is water with salt in it, therefore, it is heavier (for a given volume) than fresh water, which is water without salt!! 1 litre of fresh water weighs approximately 1 kg while salt water is more like 1.04kg per litre. This increased weight means the salt water has a greater upward or buoyant force.

Archimedes principle states that an object will float or sink depending on the weight of water it displaces. If the weight of water the object displaces is more than its own weight, the object floats, while if the weight of the water displaced is less than that of the object, it sinks.

So, imagine our 80kg diver is neutrally buoyant in fresh water. This is because s(he) displaces 80 litres of water giving an 80kg buoyant force counteracting the 80kg down force.

If we move our diver to the sea, the additional weight of the salt in the water causes the buoyant force of the water to increase to approximately 83.2kgs, (80 x 1.04) which is greater than the 80kgs down force of our diver, making them more buoyant and in need of a few extra weights.

Neutral Buoyancy in Salt Water Caves

However, the amount of salt in the sea varies depending on where in the world you are. Even diving in the Mediterranean, the seawater is much more salty around Cyprus than around the Western Med and of course, diving in the Dead Sea would require an awful lot more weight than pretty much anywhere else. So this isn't exactly a science that can be mathematically computed pre-dive.

Tried and tested is to get in the water, do a weight check and scuba dive. You will eventually get the knack for guess-timating the weight that you will need as your environment and diving equipment changes.

Artificial Reefs- What are they and Why do we want them?

Happy New Year to everyone reading the Blog. We hope 2014 is going to bring prosperity and good health to you all.

Things have started extremely well here in Cyprus with the Sinking of another Wreck to create an Artificial Reef (ok, so it went down on 20th December 2013 but who's counting?).

Our first wreck in Protaras, the Liberty, was sank in 2009 and has proved to be quite popular among divers
and fish life alike. However, the area was never closed off to fisherman, and as fast as the fish came in, they were swept back out again.

Now the Nemesis III has been sank in the same area and there is talk of a no-fishing zone being established around the wrecks to create a marine park, hopefully protecting the fish until they reach maturity and start to spill over.

What is an Artificial Reef and Why do we want them?

 An Artificial Reef is defined as "any human made underwater structure". They are usually made to promote fish life, control erosion etc. and although many people consider them to be relatively new, there are examples of Artificial Reefs being created by the Japanese back in the 1600s.

There are many objects that can be used to create artificial reefs but usually, they are items that are built but no longer fit for another purpose such as; cars, rigs and boats.

The benefits of the Artificial Reefs vary from economic to social to environmental.

Environmentally, an artificial reef can help to calm waters and influence currents, creating shelter and protection for fish life. It also serves as a visual reference for fish as they forage away from the reef itself. The development of the reef usually begins with the attraction of smaller organisms (barnacles, algae, sea squirts, bait fish) and the presence of these gradually attracts the larger pelagic fish. This in turn allows the rehabilitation of stressed natural habitations and can help to boost many fish species.

Socially and economically, the presence of artificial reefs can help to create jobs and funding in the area.

As an example, Plymouth in the Uk saw an annual increase of over a million pounds in the local economy, supporting jobs and tourism.

The fishermen also benefit, as when the fish populations increase, there will be more catch. This must be done responsibly and sustainably though, so we would hope for a no fishing zone implemented and enforced around the reef to give the fish the opportunity to grow and mature.

In fact, the only dis-advantages of artificial reefs seem to arise when they are not implemented correctly (reef item is light enough to be carried away by tides and cuurents or not cleaned correctly).

So, the pros are clear to see. Particularly in an area such as Cyprus where we have such a wide variety of fish life that is stunted by over fishing. For us Divers, any new underwater playgrounds with fish we can gaze at with envy as they swim gracefully with ease through the ocean, are a bonus where we could spend hours, if we could.

Let's hope the authorities see the benefit of the no-fish Zone around our new Wrecks and Reefs and police the area while continuing to add to the great work they have started.

Maybe 2014 will be the Year of the Fish in Cyprus

5 things that should be on every diver's christmas list

December is finally here and Christmas will soon be upon us, so I thought this would be a great opportunity to give those Divers that are not sure what to ask Santa Clause for, a couple ideas for their stockings.

Now, some of these things are on my christmas wishlist, while some are items that just got me so excited, I had to buy them in advance. However, all of them are pieces of Diving kit that will feed that need that Divers of all different certification levels get when they see new diving toys!

Here we go...

1. The Pathfinder Rebreather.

It is at the very top of my Christmas wish list this year and I am trying to be a really good boy so that Santa says "yes".

If you have been up to date with our blogs, you will know that a couple weeks ago, I was lucky enough to "try-dive" this fantastic little Rebreather (if you missed it, check it out at this Pathfinder Rebreather Blog Post) and I have wanted one ever since.

Made by the same guys that made the Megalodon CCR, the Pathfinder is a much smaller and lighter Rebreather aimed at the travelling diver or those slightly smaller in stature but to the same high quality that Divers have come to expect from this company (ISC).

2. The Shearwater Petrel.

If you are considering a CCR, then you will need a diving computer that will accommodate this... Enter the Shearwater Petrel.

Little Brother to the Shearwater Predator and descendant of the Pursuit, the Petrel is a smaller sized computer that is open for Trimix and CCR use alongside normal air and nitrox, if you aren't a Technical Diver.

The Petrel sports a 2.4 inch HD screen, which shines brightly in the darkest of caves or shipwrecks, is user customisable and adjustable. The menus are simple to use and highly intuitive, especially important on deeper dives where narcosis could be an issue. You can use up to 5 different gas mixes and swap at the touch of a button.

3. Halcyon Traveller Wing.

In this day and age of technology, the world has become a much smaller place and, as divers, we can easily travel from the UK to Thailand to Egypt to Cyprus for Scuba Diving. 

The only drawback for the travelling diver is the cost of baggage transporting all your Scuba Equipment from one destination to another.

Thankfully, manufacturers have started to bring out a number of items for the travelling diver and for those who want to dive with a single tanks set-up, there is no better travel buoyancy control device (BCD) than the Halcyon Traveller Wing

The Halcyon Traveller combines the simplicity of small jacket systems with the performance of back-mounted BC systems. It uses a unique PA6 Nylon backplate and has an integrated single-tank carrier and Cinch quick-adjust system. The shoulders and back are padded and this provides unparalleled comfort with a 30lb lift capacity.

Weight Belts are not needed with this fabulous piece of equipment, as there is a specialised weight attachment system, allowing weights to be distributed across the diver's back rather than the waist.

All of this combined with a number of other unique design features means the Halcyon Traveller BC System weighs in at less than 3kg. A must for the Diver on Tour!

4. Full Set of Miflex Hoses.

Miflex Hoses are flexible and durable and a great alternative to the usual rubber hoses that are commonplace on Scuba Diving Equipment.

They have an average lifespan of three times longer than traditional hoses, excellent resistance to abrasion with a Kink-resistant design. You can even tie an XTREME hose into a knot and air flow remains continuous.

These hoses also have a burst pressure more than twice that of traditional hoses and since they are available in a multitude of colours, such as; Green, Black, Red, Purple and Glow in the Dark Yellow to name just a few, you can stay colour coded and at the height of fashion.

Miflex are currently running a "Pink Tank" promotion, which means that miflex will donate £1 to Project Pink Tank for every Pink, Red, White or Purple Hose they sell.


 



With 30 individual safety tests performed on every hose, Premium Packaging that doubles as a water-resistant document wallet and all hoses approved and certified to EN250 Standard, why are you still in rubber?




5. A Diving Holiday.

This one is always at the top of the list and although we live in Cyprus and get to enjoy year round diving here in the balmy waters of the Mediterranean sea, it is always nice to get away and dive somewhere new

Maybe this year, our holiday diving will be in the somewhat cooler waters of the UK, at Stoney Cove and/or we might get to travel somewhere more exotic like Egypt's Red Sea or the Canaries

Top of our travel list, you will find the Galapagos, where you can supposedly find all kinds of aquatic life including Dolphins, Whales and penguins etc but I think that will have to wait until we win the lottery. I mean, even Santa Clause has his limits



So, for me, these items are some of the best on the market at the moment. There are always new toys available and something else exciting that we want and this list could have been 100 items that scuba divers would want for christmas but I guess we shouldn't be greedy. After all, christmas is a time to give...so if you are listening friends and family, I give you the gift of knowledge. You can give me anything on this list