The SCUBA thread

[qwerty007]

Originally Posted by HugoHackenbush

OK, qwerty007, this is primarily for you, but others can dive in.

My training, being long ago, consisted of a weeks worth of schooling, classroom in the morning (learning about the partial pressures of gasses etc.) and extensive pool sessions in the afternoon(endless buddy breathing, up and back, up and back).

Now the equipment was much less reliable then, and diving was still considered a "macho" sport. But still, today you can take a resort course, in the pool in the morning, dive in the afternoon. Are you confident that this short a time produces a diver that is safe?

BTW: Certifications: NAUI Scuba Diver ( back in the day one card fit all) and PADI Advanced Open Water Diver

Hugo,

This is a very valid point and bears discussing.

'Back in the day', diving was viewed, as you said - a macho sport, mainly for men and a lot of divers came out of the military system. Training was intensive, rigorous and you needed a lot of time to complete it. If you were not a strong swimmer, you need not apply.

As well, because so many divers came from the military - which used different tables (I'll explain that) that allowed decompression dives, it was quite unlike modern diving.

For the non-divers:

DECOMPRESSION DIVING

Through science (and trail and error) diving organizations have determined what the limits of no decompression diving are.

Put simply - the weight of the water puts addition pressure on the body. For each 10m (33 ft) you descend, you get an addition atmosphere of pressure. Since the body is mostly made up of water, it's really not much of a problem, as long as you equalize the pressure in your air cavities; namely your mask, your lungs and your ears.

Your mask you solve by gently blowing air through your nose into your mask, as you descend. If you don't, the worse thing that happens is you get a red mark on your face.

Your ears are equalized by performing the valsalva manoeuver. Ever few feet, as you descend, the pressure on your ear drums build up, so you hold your nose and GENTLY blow air (mouth closed) to equalize the pressure - getting them to pop. You do so early and often, until you reach diving depth, where you no longer have to perform it.

Your lungs get equalized simply by breathing.

The compressed air we breathe is 21% oxygen and 79% nitrogen (more or less, we don't count inert gases ) The thing to be careful with, is as you breathe underwater, the nitrogen is being compressed into your blood stream. The longer and deeper you stay down, the more you are absorbing.

At a certain point, you absorb so much, that you cannot safely come to the surface, without the N2 coming out of your blood and forming bubbles in your blood. You risk getting 'bent' - or as others call it, the bends.

To do so safely, you must make decompression stops along the way up, allowing the N2 to come out slowly.

Today's sport diving does not allow decompression dives and divers are supplied with tables that conservatively limit the depth and amount of time you may stay down.


Now that we've covered the background stuff, you'll see how it fits.


All dives are planned. You should know where you are diving before you go down. Let say you are diving on a wreck in 100 ft of water. You would consult your dive table, where it says START and go across to 100. Follow the column down to the black spot on the bottom. You end up at '20'.

That is the maximum amount of time, 20 minutes, that you can safely stay at 100 ft, without entering the decompression zone.

They have made these limits conservative. Because diving is related an awful lot to body physiology, the industry assumes that this is the safe limit of diving for most of the public. Maybe if you're an excellent physical specimen, it might actually be 25 mins, but this is the SAFE margin.

What the diving industry realized is that they are competing with the ski trip to Aspen, or the European vacation to Italy and every other destination where people won't dive.

They determined what the SAFE limits are for people and then began to determine how diving courses could be boiled down to the essential items needed, to make it a safe enjoyable sport FOR THE MASSES, not just the macho guys.

Now, you can get certified in 3 days, which makes it perfect for someone who is willing to spend about half of their week long vacation on diving.

To answer your pointed question - is it safe:

A lot depends on the instructor. I always tried to impress the seriousness of diving on my students. People can die, but you can also hit a tree skiing (hello Sonny Bono). When I did a resort course, I was always very aware of my students (max 4 at a time) that I was down with. I was never above hand holding - guys as well. I took my responsibility very seriously and never lost a student - and I've taught hundreds of resort courses. I never clowned around or tried to show off. Students will practice what they learned, so I always did everything slowly and carefully - hoping I would be mimicked. I think it all starts there - kinda like parenting.

Sorry for the long winded answer, but I wanted to share some background insight into the industry for everyone.

[Jeff Vader]

I finally got into Scuba diving and did my first course last May in Greece, Since then I've done a couple more courses in Honduras off Roatan island (which is great by the way). I'm heading back to Greece in May as I turn 40 and intend spending the day underwater, ideally at Santorini.

I did the enriched air, buoyancy and underwater photography courses with a view to getting a camera and using it - I've snorkelled lots as well.

Is there a camera and housing that anyone here would recommend ? I'm an ok photographer, I understand a bit about the ISO levels etc. so I'd be aiming at mid-level camera, not too high range (say 800-100 euro in total for both) as price will be a consideration.

[qwerty007]

Originally Posted by Jeff Vader

I finally got into Scuba diving and did my first course last May in Greece, Since then I've done a couple more courses in Honduras off Roatan island (which is great by the way). I'm heading back to Greece in May as I turn 40 and intend spending the day underwater, ideally at Santorini.

I did the enriched air, buoyancy and underwater photography courses with a view to getting a camera and using it - I've snorkelled lots as well.

Is there a camera and housing that anyone here would recommend ? I'm an ok photographer, I understand a bit about the ISO levels etc. so I'd be aiming at mid-level camera, not too high range (say 800-100 euro in total for both) as price will be a consideration.

JV!

Love Roatan. Did you dive Mary's Place with the swim throughs? Did you get a chance to touch Molly the Moray, as she eats out of the jug of fish? Do a night dive?

It remains one of my favorite places to dive.

Good choice to get your EANx cert - especially if you're planning on multiple dives during a vacation. Sorry, but I cannot help you with the photog stuff.

Hopefully some others can point you in the right direction.

Welcome to the thread!

q

[richardoe]

Scapa Flow in Orkney is a good place to dive Ive heard.

And someone will correct me if Im wrong,but you have 24 hours between diving and flying. So dont dive the day you fly back from holiday.

[HugoHackenbush]

Originally Posted by richardoe

Scapa Flow in Orkney is a good place to dive Ive heard.

And someone will correct me if Im wrong,but you have 24 hours between diving and flying. So dont dive the day you fly back from holiday.

This is absolutely correct. The same principles outlined by qwerty007 apply going up as they do going down. The modern pressurized aircraft make this less of a risk, but as with everything in diving, safety first.

[Jeff Vader]

Originally Posted by qwerty007

JV!

Love Roatan. Did you dive Mary's Place with the swim throughs? Did you get a chance to touch Molly the Moray, as she eats out of the jug of fish? Do a night dive?

It remains one of my favorite places to dive.

Good choice to get your EANx cert - especially if you're planning on multiple dives during a vacation. Sorry, but I cannot help you with the photog stuff.

Hopefully some others can point you in the right direction.

Welcome to the thread!

q

Did Marys place and the night dive as well - the bio-luminescence was pretty spectacular.

No worries on the camera stuff, reading on-line reviews is one thing but I'd put more faith in a summary from someone who has actively used something i.e. I've used camera x for a couple of years etc.

[HugoHackenbush]

First off, Jeff Vader and Q007...Roatan! I'm jealous. That along with Truk lagoon are my remaining dream dives.

My question about training stems from diving a long time and encountering people who were either poorly trained or have forgotten their training. Case in point, realizing my dream of diving Australia's Great Barrier Reef, there was one guy who had no idea how to make himself neutrally buoyant. He was over-weighted to start with, could not keep himself off the sea bed, and as a result was constantly flailing around and crashing into the reef. After watching this idiot damage this irreplaceable treasure for a few minutes, I swam over to him, grabbed his BC inflator and punched a couple bursts of air into his BC. Even through his mask, I could see his eyes widen in surprise as if to say "Wow, that's a lot better!" This guy had no business diving.

Actually, this guy was such an idiot, he had nearly offed himself before even getting in the water, by wading around the shoreline that had box jellyfish swimming in it, one of the deadliest creatures on Earth. The divemaster plucked one out of the water not two feet from where this guy had been wading. "This joker gets a meter of tentacle on you and you're a dead man," he said and flung it away.

[Jeff Vader]

Originally Posted by HugoHackenbush

First off, Jeff Vader and Q007...Roatan! I'm jealous. That along with Truk lagoon are my remaining dream dives.

My question about training stems from diving a long time and encountering people who were either poorly trained or have forgotten their training. Case in point, realizing my dream of diving Australia's Great Barrier Reef, there was one guy who had no idea how to make himself neutrally buoyant. He was over-weighted to start with, could not keep himself off the sea bed, and as a result was constantly flailing around and crashing into the reef. After watching this idiot damage this irreplaceable treasure for a few minutes, I swam over to him, grabbed his BC inflator and punched a couple bursts of air into his BC. Even through his mask, I could see his eyes widen in surprise as if to say "Wow, that's a lot better!" This guy had no business diving.

Actually, this guy was such an idiot, he had nearly offed himself before even getting in the water, by wading around the shoreline that had box jellyfish swimming in it, one of the deadliest creatures on Earth. The divemaster plucked one out of the water not two feet from where this guy had been wading. "This joker gets a meter of tentacle on you and you're a dead man," he said and flung it away.

Yep they are everywhere - someone who has all the gear but no idea. They spent a couple of hundred on a flash wetsuit but churn up the bottom or bounce off the walls on a swim-through.

[qwerty007]

Originally Posted by HugoHackenbush

First off, Jeff Vader and Q007...Roatan! I'm jealous. That along with Truk lagoon are my remaining dream dives.

My question about training stems from diving a long time and encountering people who were either poorly trained or have forgotten their training. Case in point, realizing my dream of diving Australia's Great Barrier Reef, there was one guy who had no idea how to make himself neutrally buoyant. He was over-weighted to start with, could not keep himself off the sea bed, and as a result was constantly flailing around and crashing into the reef. After watching this idiot damage this irreplaceable treasure for a few minutes, I swam over to him, grabbed his BC inflator and punched a couple bursts of air into his BC. Even through his mask, I could see his eyes widen in surprise as if to say "Wow, that's a lot better!" This guy had no business diving.

You're absolutely right, buoyancy is a big thing. It's also a difficult skill to master, given to many different variables.

For the non-divers:

Some basic rules of weighting


People with a higher fat content, require more weight. More muscular, requires less.

Diving in fresh water is different than diving in salt water - due to the difference in density. Salt water requires more weight.

Different wetsuits and equipment require different weighting. If you dove with 8 pounds of weight, in the Caribbean with a short sleeve wetsuit (a shorty) - then dive in colder water in a 7 mil suit with hoodie, boots and gloves, expect to add on the weight.

Depth - your scuba cylinder in linked directly to your buoyancy compensator (BCD) via a hose. Here's an image of a BCD





The rubber hose that you see over the left shoulder is the power inflator. It allows you to add or remove air from your BCD, which has a rubber bladder inside it, so that you can remain NEUTRALLY BUOYANT - that is, neither rising to the surface or bumping along the ground.

Depth is important because as you descend, the air in your BCD bladder becomes more compressed which requires you to add a touch more air. Add too much and you start to head towards the surface. (I'll get into DIVE PROFILES another time, Hugo)

Here's the other kicker;

As you begin to ascend, the pressure on you DECREASES - therefore the air in the BC expands, which can drive you to the surface even faster.

Another factor in buoyancy is your cylinder of compressed air. Aluminum cylinders weigh differently than steel cylinders. As well, a cylinder at the beginning of a dive is heavier, due to the compressed air it carries, that the end of a dive - when it is lighter.

Breathing is also a huge component of diving. As you take a breathe of air, your lungs act like airbags - causing you to slowly rise. Breathe out and you slowly sink a bit.

IN GENERAL

People tend to overweight themselves, in my experience. I guess they feel more is better.

Back to you, Hugo - absolutely!

Buoyancy is a hugely underrated skill. You can easily tell an experienced diver from a rookie usually in two ways; Swimming technique and buoyancy.

An experienced diver will be properly weighted and not mess around too much with his BCD. He won't be bumping into things or floating off to the surface. Hands held together (or arms crossed, as I do) he or she slowly paddles efficiently around - legs only, not expending too much energy.

An inexperienced diver, like Hugo's friend here - has trouble staying neutrally buoyant and usually flails around with their arms.


The reason why I listed all of the things above is to illustrate all of the components that effect buoyancy - quite a laundry list, especially for a new diver.

Yes - instruction is one component. A good instructor who takes the time and effort to walk you through every point is good. But almost as important is practice. PRACTICE. PRACTICE. PRACTICE. Not on a reef, either. Confined water or a sandy bottom is a good place to start.

It took me a good 25-50 dives at the beginning to get comfortable in the water. A hundred more before buoyancy became automatic.

[qwerty007]

Originally Posted by richardoe

Scapa Flow in Orkney is a good place to dive Ive heard.

You are correct. Many dive pubs have an issue dedicated to it, and the wrecks there.

Looks like a great place to dive...if it wasn't so blasted COLD!!!!

Brrrrrrrr....