Many divers who earn “open
water” certifications choose not to
pursue further formal training, opting
for practical experience though
their diving. This often works well
since practical experience is just as
relevant in producing a qualified
diver. At least, in warm water and not
too difficult conditions.
As divers age, their limitations
  increase: possible reduced stamina, higher blood pressure, cardiac problems,
reduced flexibility and mobility,
arthritic joints, vision and hearing
loss, deteriorated muscular strength,
postoperative limitations, side effects
of medications, and general reduced
physical fitness. Of course, there are
exceptions, but for nearly all, as a
diver ages, limitations increase that
can affect their fitness to dive.
  
    | Often I’ve been deceived ... On trips I had a 46-yearold in such poor condition that even without her equipment
 on she couldn’t climb up the ladder without assistance
 . . .a morbidly obese 55-year-old who couldn’t
 reach down to put on his own fins;
 | 
Even so, older sport divers with
  increasing disposable income often
  seek more challenging diving, ranging
  from the deep wrecks of Bikini
  to the wilds of the Galapagos. Most
  often, typical sport diving experience
  is insufficient. In fact, it often
  produces what I call the Into Thin  Air mentality, referencing the fatalities
  that occurred during the May
  1996 expeditions to the summit of
  Mt. Everest as chronicled in Jon
  Krakauer’s book of the same name.  
There were amateur climbers on
  the mountain who shouldn’t have
  been there. Yet they had the money to pay the hefty expedition fees and
figured the alpine guides would look
after them despite their limitations.
One wealthy New Yorker even paid
extra to be “short-roped” to the summit,
where she had a Sherpa essentially
drag her up the face of Everest
on a tether. When the weather turned
unexpectedly severe, several amateur
climbers died along with the professional
guides accompanying them.
Diving Beyond One’s
Capabilities
Of course, well intended, but
  under-qualified folks sign up for diving
  trips beyond their capabilities.
  Most operators screen applicants in
  advance. Typically, they require an
  applicant to detail their training,
  diving experience, medical history,
  fitness to dive, etc. However, some
  eager divers misrepresent their diving
  skills or medical fitness. The problem
  is compounded because operators
  have the economic need to get
  customers for these expensive trips.
  So sometimes unsuited divers make
  the journey. Some get injured. A few
  don’t return. The lucky ones have
  close calls or get scared out of their
  wits when they can’t cope with the
  harsh conditions.  
I’ve had divers on rebreather or
  deep dive trips whose applications
  looked suitable and they came across
  convincingly in phone interviews.
  Yet, often I’ve been deceived. On
  trips I’ve had a 58-year-old who didn’t
  find it necessary to reveal that he
  had only one lung; a 46-year-old in
  such poor physical condition that
  even without her equipment on she
  couldn’t climb up the ladder without
  assistance; a 64-year-old with four
  cardiac events in the last two years;
  a morbidly obese 55-year-old who
  couldn’t reach down to put on his
  own fins; a 52-year-old taking three
  antidepressant medications who had
  recently attempted suicide; and a
  57-year-old in such poor shape he
  couldn’t swim 20 ft.  
While these cases were daunting,
  they were unknown to us until
  we had to engage in rescues. But
  the worst offender was a 26-year-old
  male in great shape who signed up
  to dive rebreathers at Cocos Island.
  We require a minimum of 150 logged
  dives, experience on live-aboards,
  current experience, Nitrox certification,
  and decompression ratings. He
  claimed to have all and promised to
  bring his Nitrox card with him. He
  showed up with a forged Nitrox card
  (determined later) and a “pencil
  whipped” log book showing 200-some
  dives in a variety of challenging conditions,
  and appeared to meet our
  criteria. Only when he had trouble
  assembling his scuba gear before an
  orientation dive and could not figure
  out how to read his computer did he
  finally confess that he had just completed
  his basic scuba training and
  had only done seven dives. He figured
  diving at Cocos was just another
  extreme sport merit badge that he
  could bluff his way through and
  the staff would babysit him through
  any problems. We shut him down
  completely and he spent ten days at
  Cocos getting a suntan but not getting
  wet.  
It’s exciting to expand your diving universe. But the ocean is a
fickle mistress and you won’t master
her without specialized training.
And you owe it to yourself and to
the dive operator to be honest about
your experience and limitations. You
can bluff but that doesn’t help once
you’re underwater. So, you hiked
up Mt. Rainier on a sunny July day.
That doesn’t qualify you to climb Mt.
Everest.
Furthermore, incapable divers
  can also risk the lives of fellow divers
  who may forsake their safety to rescue
  them. I once had to break off my own
  decompression to surface and rescue
  a diver who had incurred a deco
  obligation and then surfaced anyway
  because he couldn’t understand
  his computer readout. Ironically,
  although I dragged him back down to
  complete his deco and an extra margin
  for his omitted stop, he emerged
  unscathed. I got bent. Luckily, the
  vessel had a great supply of oxygen
  and I could treat myself in the field.  
And, if they don’t put a fellow
  diver at risk, they can certainly ruin
  a dive trip for everyone else. When
  a boat has to cut short an expensive
  trip to return an injured diver to
  port, a diver who shouldn’t have been
  there in the first place, it is not a
  happy outcome.  
The Step to Technical Diving  
Rebreather diving is the rage. By
  comparison, open circuit equipment
  is simple and relatively foolproof.
  If you don’t turn the valve on, the regulator won’t breathe. But you can
actually breathe through the closed
or semi-closed loop rebreather without
turning on the gas supply. There
is no warning that things are amiss
until you pass out from hypoxia.
Rebreathers have demanding and
unforgiving maintenance regimens
as well as lengthy check lists before
diving. If you’re unwilling to handle
the technical demands then stay with
open circuit.
Not long ago, the Okeanos
  Aggressor, Sea Hunter and Undersea
  Hunter offered onboard rebreather
  rental and training programs during
  their 36-hour crossing to Cocos
  Island. However,the problems of first
  time users were frequent and severe.
  Now divers must not only bring their own rebreathers, but also provide
proof of certification and credible
records of logged dives.
If you want to dive deep wrecks,
  you need formal training for deep
  dives. First, you’ll quickly learn
  whether your physical condition is
  acceptable. Then, you’ll find out
  with an instructor at hand whether
  you can mentally and physically manage
  the dives. But not all advanced
  technical courses are equal. Some
  amount to little more than a few
  dives in benign settings with an
  instructor looking on. I’ve got a long
  track record with both the TDI and
  IANTD programs, whose instructors
  must evaluate divers realistically
  before they’re allowed to train them
  – some divers get excluded – and
  then monitor them closely throughout
  the training.  
Deeper diving and rebreather
  diving typically require decompression
  and proper training. With open
  circuit scuba, the safest gas is Trimix,
  but in some remote areas like Bikini
  only air is available. This decreases
  bottom time, increases decompression
  time, and increases the risk of
  narcosis. Since narcosis affects each
  diver differently, in training you learn
  your narcosis tolerance so you can
  establish a proper dive plan.  
Trimix diving requires specialized
  training, as does decompression diving.
  A record of doing “safety stops”
  will not give you the skills to hit
  multiple stops, switch gases, execute
  precise ascent rates and handle contingencies
  where escape to the surface
  is not an option. Expecting to
  go deep and stay long at Truk is not
  for untrained divers.  
If you use double cylinders, you
  need the strength to tote them and
  the ability to swim with the increased
  drag and weight. Backup regulators,
  stage cylinders, surface marker lift
  bags, deco bottles, etc. can create a
  daunting amount of gear to manage,
  while requiring skill, flexibility and
  strength. Wreck penetration requires
  lines, reels, and possible staging of
  exit cylinders. The record of unqualified
  divers lost inside wrecks due to
  narcosis, silting, or simply getting disorientated
  from multiple turns down
  passages is too long to cite.  
Areas such as Cocos or Malpelo
  islands require a diver to roll off an
  unanchored dive launch with no
  descent line and drop through a
  ripping current to 60-120 feet, then
  get established on the bottom or be
  swept into the blue. Dives proceed
  to a series of stationary observation
  points for marine life, with
  drifts between set points. Current
  diver skills and compass or natural
  orientation skills are essential to
  arrive underwater where the action
  is. Finally, the dive often ends with
  a long drift in the blue for a safety
  stop, perhaps even decompression.
  For the inexperienced, dives like this
  can be terrifying and stressful. Even a
  fit diver cannot maintain a headway
  against more than about a one-knot
  flow for long. Add in the vagaries of
  updrafts and downdrafts and we have
  the ingredients for disaster if you’re
  not comfortable with such conditions.  
Truth Always Wins  
Thirty-five years ago, I was part of
  a Navy deep diving team filming submarines
  passing by us at high speeds
  from about 20 feet away. The diving
  officer reminded us that the key to
  the generous retirement program
  was surviving that long. It was good
  advice then. And still is.  
So, don’t be in denial about
  your own physical limitations, training
  and skills and be honest when
  you sign up. Sometimes the most
  valuable lesson to be learned is that
  you shouldn’t place yourself in an
  environment that exceeds your ability
  or comfort zone. You must have the
  independent skills to deal with contingencies
  entirely on your own. The
  only help you’ll get will come from
  your conditioning, training and skills
  – and the decisions you make. After
  all, the ocean is a fickle mistress.
Author Bret Gilliam has been professionally
involved in diving since 1971 and has
logged more than 17,000 dives. He was the
founder of Technical Diving International
(TDI). He also founded Fathoms Magazine
and leads exotic dive expeditions worldwide.
He lives on an island in Maine and travels
on dive projects six months of the year