Article: Randall Munroe (xkcd) on swimming with spent nuclear fuel rods

Randall Munroe, the man behind the xkcd cartoons that light up my world, blogs about ridiculous and unlikely scenarios at What If? He uses his physics knowledge and some wide-ranging research to answer hypothetical questions that couldn’t be answered with an experiment or by direct inference from actual events.

Scenario 29 answers the question:

What if I took a swim in a typical spent nuclear fuel pool? Would I need to dive to actually experience a fatal amount of radiation? How long could I stay safely at the surface?

It turns out that, as long as you stayed far enough away from the fuel rods while in the pool, you’d probably experience a lower dose of radiation than you would walking around outside the pool. The amount of radiation in the water halves with every seven centimetre increment away from its source. Divers are actually employed to perform tasks and service the equipment in these pools, so it can’t be that dangerous. There is a description of an accident, however, and it makes fascinating reading (follow the link too).

Read the scenario here.

Mask remove and replace

Kirsten taking off her mask in the pool
Kirsten taking off her mask in the pool

Mask remove and replace is a skill that some find quite tricky, but once you’ve relaxed, adjusted your mind to the fact that you probably aren’t going to see much when the mask is off, and told yourself that water isn’t going to go up your nose, it’s not too difficult to master.

It’s not something you’ll have to do in the course of a routine dive, but it’s to prepare you for the event when your mask strap breaks, a fellow diver kicks your mask off, or your mask floods for some other reason (such has excessive hair inside the seal). Wearing a hoodie definitely helps with the “replace” part of the equation, as the strap goes on easily.

No mask breathing

Just thought I’d share this photo of Kate taken early last year when she was in Cape Town preparing for her Instructor exams. Firstly, the way she has all her gear tucked in and organised around her body is something that new divers should try to emulate. Dragging octos and pressure gauges mean expensive repairs and servicing, not to mention the damage that this equipment does to marine life and reefs.

Kate has a zen moment
Kate has a zen moment

Secondly she’s practising no-mask breathing, a skill which might make you want to panic, but is actually not that difficult once you relax and realise that water isn’t going to flood up your nose when you take your mask off. Think of swimming in the pool before you learned scuba – water doesn’t go into your nose unless you actually use your nose to inhale. Which in this case is obviously a no-no!

Guest post: Kate’s IDC

Kate practising a no-mask swim in the pool
Kate practising a no-mask swim in the pool

Many of the divers who regularly dive with me will know Kate, who came out to South Africa for two months in late 2010 to qualify as a Divemaster. She had never dived before when she arrived, and I took her through a full Zero to Hero course, including 60 dives to meet the requirements for Divemaster, before she went back to the UK.

She returned to South Africa in April (her family joined her here for a short holiday) to prepare to do an Instructor Development Course, for which she had to get her dive numbers up to 100 dives. She did her IDC with Danny Martin, who trained me and who I rate as one of the best Instructor trainers in South Africa. We asked her to write about what the IDC involves so that those of you who are curious can get an idea of how one works.

The PADI IDC is an instructor development course that consists of two halves, the first (three days) is Assistant Instructor and the second is Open Water Scuba Instructor (four days). The final two days are when the Instructor Examination (IE) takes place. An examiner is brought in from somewhere else (usually outside the country) to test the candidates. We also spent an extra day doing the EFR Instructor course.

I undertook my IDC with Danny Martin at Coral Divers, Sodwana Bay, South Africa.

The programme consisted of completing;

  • An exam (made up of 5 parts: physics, physiology, environment, equipment, and standards and procedures)
  • Prescriptive teaching presentations (taking a knowledge review question and expanding on it so as to help students understand the answer in more depth)
  • Confined water presentations (giving a pre-dive briefing, demonstrating the skill, having the student demonstrate the skill and then giving a debriefing)
  • Open water demonstrations (same procedure as in confined water, except that the Instructor does not demonstrate the skill this time)
  • Watching risk management and marketing presentations
  • Testing our own skills in the pool, for ease of understanding and ability to demonstrate
  • Rescue workshops

The main aspect of the IDC is preparation. After completing my Divemaster course with Tony, he then made sure I fully prepared for the IDC. There’s not a lot of new information to learn as most of it is covered in the Divemaster program but having someone to test me on everything was rather handy. Tony also took the time to do one to one pool sessions in which he would make sure my skills were above the standard needed. He also ran me over what to expect from the IDC and how to prepare myself.

Sodwana was a great place to complete my IDC. The environment is really friendly and the diving is exceptional (it was a minimum of 26 degrees at all times!). The accommodation is tents or wooden cabins, and they have a bar and a restaurant. There is a tractor service to take you to the beach every 45 minutes.

I definitely would recommend doing the IDC, for me it has opened up a new love for diving. It takes you further then being just a Divemaster and gives you more responsibility within the diving community. You also find that the experience increases your diving ability and performance.

I started diving in October 2010 with my Open Water and completed my IDC in June 2011. I also completed a load of specialties and am now preparing myself for a trip to the Arctic circle.

Kate is now a PADI Open Water Scuba Instructor. When she has done 25 certifications, she will be certified as a Master Scuba Diver Trainer – this means she can teach courses from Discover Scuba Diving and Open Water up to Divemaster, along with a list of Specialties. I am very proud of Kate and really enjoyed teaching her. She impressed (and often wildly amused) everyone who met her while she was in South Africa and she will be a great ambassador for diving. I am looking forward to following her adventures!

Directions to the Northern Suburbs swimming pool

Tony sometimes uses the swimming pool at one of the dive shops in the northern suburbs, Scuba Centre (Shop 1 Tyger Quays, Tyger Waterfront) to do the confined water skills for the Open Water course.

Kirsten in the pool
Kirsten in the pool

Here are directions to get there:

Coming from Cape Town south:

  1. Get onto the N1 northbound from Cape Town.
  2. Take the Willie van Schoor/Tyger Valley exit number 23 off the N1.
  3. Tturn left into Willie van Schoor road.
  4. Take the first left into Mispel road.
  5. At the T junction, turn right into Carl Cronje drive.
  6. Turn left into the Tyger Waterfront. The water-filled quarry should be on your right.
  7. Go through the first traffic circle inside the Tyger Waterfront.
  8. Scuba Centre is on your right – there is parking in front of the shop.
  9. Look for the divemobile parked outside (Tony’s big black van with scuba diving written all over it)

Coming from the Northern Suburbs:

  1. Get onto Carl Cronje drive heading south towards the N1.
  2. Pass Willowbridge Shopping centre and Tyger Falls.
  3. Before you get to the N1, turn right into the Tyger Waterfront. The water-filled quarry should be on your right.
  4. Go to item 7 above and continue from there.
Dean in the corner
Dean in the corner

This is what the entrance to Tyger Waterfront looks like:

Directions to the Southern Suburbs swimming pool

If you learn to dive with Tony (which you should, if you haven’t already) you will do your confined water skills at our pool at our facility in Sun Valley. You might also do a Discover Scuba DivingBubblemakers (if you’re a kid), or Seal Team course at the pool.

We used to use 2 Military Hospital swimming pool on Wynberg Military Base. It’s indoor, and heated to about 24 degrees. The water quality varies wildly, with visibility from 3-25 metres.

The pool is on the corner of Buren and Scobel roads in Wynberg and is run by SwimLab. Once you’re inside the Military Base, just follow the signs for the hospital.

Here’s how to get there:

From central Cape Town (or anywhere north of Wynberg):

  1. Get onto the M3 towards Muizenberg.
  2. At the top of Wynberg Hill take Exit 12, to Trovato Link Road.
  3. Follow Trovato Link Road through a set of traffic lights.
  4. At the second traffic lights, turn right into St John’s Road.
  5. Where the road forks, take the left fork into Camp Road.
  6. Turn right into 51st Avenue.
  7. Take the first left into Brink Drive.
  8. Follow Brink Drive to the T junction with Buren road, and then turn right.
  9. Look for Scobel Road on your right – the pool is covered with a domed white plastic cover and will be on the corner.

From anywhere else:

  1. Get onto the Main Road heading towards Wynberg.
  2. Turn into Constantia Road from whatever direction you’re approaching from.
  3. Go through the traffic circle at the Engen garage, taking the second exit (so you’re still going in the same direction).
  4. When you can see the police barracks in front of you (large, unsightly blocks of flats), turn right up Bower Road.
  5. At the top of Bower Road, turn right at the traffic lights.
  6. At the next set of traffic lights turn left into St John’s Road.
  7. Follow the directions from point 5 above.
Inside the pool area
Inside the pool area

Seal Team

PADI has an amazing program for young kids. It is called Seal Team and it is a program in which 8 – 10 year olds can learn to dive.

Abby giving an OK sign
Abby giving an OK sign

My latest junior dive star is nine years old. Abby, on vacation from the UK, wanted to learn to dive with her older brother and sister plus mom and dad. The five of them spent two days in the pool and in these sessions Mom, dad and older brother and sister completed their confined skills for Junior Open Water and for the parents, Open Water diver.

Abby writes on a slate underwater - look at that buoyancy
Abby writes on a slate underwater - look at that buoyancy

Abby completed five dives and five Aqua Missions thus resulting in her being certified as a PADI Seal.
At the age of nine her buoyancy was excellent, she swam through hoops , cleared a flooded mask, recovered her regulator and used an alternate air source.

Writing on the wall
Writing on the wall

We also played games with hoops and slates and she used an underwater camera to take a whole lot of paparazzi photos of her family while they were all diving! The Seal Team crewpack contains a DVD and a manual/logbook with quizzes, puzzles and lots of information. It’s definitely not a Mickey Mouse course – and it’s a lot of fun both to teach and participate in.

Seal Team manual/logbook
Seal Team manual/logbook


Friday was spent at the Virgin Active pool in Claremont, in crystal clear warm water. The pool is heated and I would guess it was around 24 deg celsius. We had a great time with a bunch of kids, conducting PADI Bubblemakers programs. We also had a couple of DSDs and all round good fun.

Going through the Bubblemakers/DSD flip chart
Going through the Bubblemakers/DSD flip chart

It is amazing at how quickly kids take to scuba diving. The youngest participant was eight years old and they become so amusing and small looking when you strap a 10 litre cylinder to them. Even the smallest mask looks huge on an eight year old head and the neat small mouthpieces we use as adults fill their mouths to a point that they seem like chipmunks. Within 15 minutes they had good buoyancy, understood the signs and signals and swam the length of the pool several times picking up small tiles and other odds and ends in the water.

Underwater exploration in the pool
Underwater exploration in the pool

If you want your children to be safe and comfortable around water then the Seal Team program is an extremely good way to achieve this. It follows on from Bubblemakers and can be done from the age of 8 years. They become real scuba divers, have a chance to perform navigation, search and recovery, underwater photography and a few other exciting skills.

Imagine how good your underwater skills would be today if you started when you were eight!!