Are You Fit Enough to Dive?

A peer-reviewed study published this year analysed every recorded Australian scuba diving fatality from 1972 to 2021. Four hundred and thirty deaths. Fifty years of data. The findings are not particularly alarming if you are young and fit. They are very relevant if you are over 45, which describes a large and growing share of Melbourne's recreational diving community.

The study's core message is not that diving has become more dangerous. The average diver is more experienced, better trained, and more likely to be diving with a buddy than ever before. The message is that the nature of the risk has fundamentally shifted, and the old framing of diving fatalities as a skill or equipment problem no longer fits the data.

What the Study Found

The paper, authored by John Lippmann of the Australasian Diving Safety Foundation and Monash University's Department of Public Health, compared two periods: 1972 to 1999 (when diving was expanding rapidly in Australia) and 2000 to 2021 (the modern era). The shift between the two periods tells a specific story.

The Divers Who Are Dying Are Older

The median age of fatality victims rose from 33 to 47 years between the two periods. In the earlier period, divers aged 45 and over accounted for 24 percent of all fatalities. In the modern period, they account for 57 percent. The typical victim in 2021 looks nothing like the typical victim in 1975.

They Are Also More Experienced

This is the finding that challenges easy assumptions. In the earlier period, 64 percent of fatal accident victims were certified divers. In the modern period, that figure rose to 81 percent. More victims also had a dive buddy present at the time of the incident, up from 17 percent to 27 percent. The people dying are not beginners who panicked on their first open-water dive. They are experienced, certified adults who had dived many times before.

The Cause of Death Has Changed

In the earlier period, drowning or asphyxiation was the primary cause in 47 percent of cases, and cardiac-related causes accounted for 12 percent. In the modern period, drowning fell to 36 percent while cardiac-related deaths more than doubled to 26 percent.

Cause of Death	1972 - 1999	2000 - 2021
Drowning / asphyxiation	47%	36%
Cardiac-related	12%	26%
Pulmonary barotrauma / AGE	19%	12%

The shift from drowning to cardiac events is not because drowning prevention has improved so dramatically. It is because the demographic of the diving population has aged, and older divers carry a higher burden of cardiovascular disease - much of it undiagnosed.

The Cardiac Picture

Of the 30 cardiac-related fatalities examined in detail in the study, 20 involved severe ischaemic heart disease. In the majority of those cases, the condition had not been diagnosed before the fatal dive. These were people who did not know they had a serious heart condition.

This matches what DAN's global fatality data has been showing for years. Among recreational divers who died and underwent autopsy, 51 percent had significant coronary atherosclerosis and 60 percent had cardiomegaly, left ventricular hypertrophy, or cardiomyopathy. DAN research shows that divers over 50 face a cardiac-related fatality risk 10 to 13 times higher than divers under 50.

The study also found that 43 percent of victims with recorded body mass index data were classified as obese (BMI above 30). That is meaningfully higher than Australia's general adult obesity rate of around 31 percent, suggesting obesity is a specific contributing factor rather than a background population characteristic.

Why Cold Water Makes This Worse

Melbourne's Port Phillip Bay and the Mornington Peninsula run at 9 to 14°C for most of the year. That cold water creates a specific physiological challenge that is directly relevant to cardiac risk, and it is one that warmer-water divers do not face to the same degree.

When the body is suddenly immersed in cold water, two competing reflexes activate simultaneously. The cold shock response triggers sympathetic activation - the heart rate accelerates and blood pressure spikes sharply. At the same time, the diving reflex (triggered by facial immersion) activates parasympathetically, attempting to slow the heart. These competing signals - speed up and slow down simultaneously - create what is called autonomic conflict, and this conflict is a recognised mechanism for triggering dangerous cardiac arrhythmias.

This window is most dangerous in the first 30 seconds to two minutes of immersion. It applies even when wearing a dry suit if the face or hands are briefly exposed. For a diver with pre-existing but undetected coronary artery disease, the additional cardiac workload from cold-induced vasoconstriction can be enough to trigger a myocardial infarction. Cold also compounds equipment workload: a 7mm wetsuit is more restrictive than a thin tropical suit, a dry suit adds buoyancy management demands, and cold air from the cylinder itself can trigger bronchospasm in anyone with underlying airway sensitivity.

None of this is a reason to stop diving in Melbourne. It is a reason to know your cardiovascular health before you do.

What "Fit to Dive" Actually Means

Dive fitness is not the same as general fitness. The SPUMS (South Pacific Underwater Medical Society) guidelines set a minimum sustained aerobic capacity of 6 METs for recreational divers. To put that in practical terms: 6 METs is roughly equivalent to a sustained brisk walk at 6 km/h, casual cycling on flat ground, or swimming laps at a comfortable pace. That sounds modest. The issue is that a diver swimming against a moderate current, managing an emergency ascent, or assisting another diver can reach 10 to 12 METs - and they need the cardiac reserve to handle that without incident.

A diver who cannot comfortably sustain 6 METs does not have an adequate aerobic reserve for safe diving.

The study noted a separate and worsening problem: BCD inflation failures increased from 23 percent in the earlier period to 32 percent in the modern period. More victims failed to activate their buoyancy device in a crisis. This is a fitness and familiarity issue as much as a training one - a diver who is already cardiovascularly stressed during an emergency is less able to execute the right response.

A Simple Practical Self-Check

Before returning to open-water diving after a winter break, four things give a useful indication of whether your functional fitness is where it needs to be:

• Swim 400 metres continuously at a comfortable pace without stopping. The minimum certification standard is 200 metres, but that leaves no margin for an unplanned emergency requiring sustained effort.
• Tread water for 10 minutes fully geared up, or simulate the equivalent load.
• Walk 30 metres and climb a 1.5 metre ladder in full kit without becoming noticeably breathless.
• Heart rate recovery test: after sustained moderate exertion (swimming 200 metres at a working pace), your heart rate should return below 100 bpm within two minutes. If it takes significantly longer, seek a medical review before the next open-water dive.

None of these require specialised equipment. They require honesty.

Conditions That Require Medical Review

The SPUMS cardiovascular guidelines are specific about several common conditions in the 45 and older age group.

Hypertension: Blood pressure above 160/100 mmHg is a contraindication to diving until investigated and treated. Controlled hypertension on medication can be cleared for diving, but the specific medication matters - diuretics affect hydration (and therefore DCS risk), and some beta-blockers reduce exercise tolerance in ways that are relevant to diving. Any antihypertensive medication should be reviewed by a SPUMS-accredited doctor in the context of diving.

Asthma: The old blanket prohibition has been replaced by a conditional framework, but any asthma that is triggered by cold air, exercise, or emotion remains a contraindication. Cold air from a scuba cylinder at depth can trigger bronchospasm - this is a direct risk in Melbourne's conditions. All divers with asthma require individual medical assessment before diving.

Arrhythmias: Atrial fibrillation can be cleared for diving in some circumstances, but most AF patients are on anticoagulation therapy, and anticoagulants are themselves a contraindication due to barotrauma risk. Anyone managing an arrhythmia should discuss their specific situation with a diving medicine specialist, not their GP.

Post-COVID: Any COVID-19 illness with cardiac or pulmonary involvement requires a minimum three-month waiting period and clearance via echocardiography and exercise ECG before returning to diving. Even mild symptomatic illness requires at least 60 days from a negative test result, and medical evaluation.

Getting a Dive Medical in Melbourne

Australian Standard AS4005.1 sets the framework for recreational dive medicals, and it requires the assessment to be performed by a practitioner trained in diving medicine. A standard GP visit does not constitute a dive medical in the AS4005.1 sense - the conditions relevant to diving (barotrauma, DCS risk, cold immersion, nitrogen narcosis) require specific knowledge that most GPs do not have.

SPUMS recommends that all divers aged 45 and over have an assessment at least every five years, with emphasis on cardiovascular fitness. The study's author puts it more directly: the shift in the fatality data suggests the recommendation should be acted on, not filed away. For divers in this age group who have not had a dive medical in the past few years, this winter is the right time.

The SPUMS website at spums.au has a practitioner finder searchable by state, and divemedicals.com.au is set up specifically for AS4005.1 assessments. An initial assessment for a diver aged 45 and over typically includes a resting ECG, a cardiovascular risk score (using the Australian CVD risk calculator), and depending on your risk level, possibly a coronary calcium score or stress test.

What to Do This Winter

The winter off-season is genuinely the best time to sort this out, not because diving is unavailable (Melbourne diving continues year-round), but because this is when most recreational divers are diving less frequently, training motivation is lower, and the question of whether you will be ready to dive well when conditions improve is worth answering now rather than at the boat ramp in September.

Pool training: Melbourne Freedivers Club runs pool sessions at MSAC Albert Park on Monday and Thursday evenings, and at Victoria University Footscray on Wednesdays. Diving Victoria-affiliated clubs including Ringwood Diving Club, Whitehorse Diving Club, and ACD Elite Diving all run programs with pool components. Pool training directly builds the aerobic fitness and water comfort that open-water diving demands.

Fitness baseline: Three to four sessions per week of sustained aerobic exercise at a working intensity - swimming, cycling, brisk walking, or anything that gets your heart rate to a training level for 30 to 60 minutes - is the foundation. Specific strength work for equipment carrying and ladder climbing is secondary but useful. Core work improves trim and buoyancy control in a way that reduces exertion on actual dives.

Before returning to open water: Do a skills-refresh pool dive before your first open-water dive of the season. Not to check off certification requirements, but to rebuild BCD and buoyancy familiarity, recalibrate your weighting after a period without diving, and do a cold-water entry without the pressure of a site-specific dive agenda. The study's finding that BCD inflation failures increased significantly over the past two decades suggests that equipment familiarity deserves more regular practice than most recreational divers give it.

The Broader Point

The Lippmann study is not a reason to stop diving. It is a reason to take the pre-dive medical seriously, to be honest about your fitness before an open-water session, and to understand that the risk profile of recreational diving in Australia has shifted from a training and equipment problem to a health and fitness one. The deaths that are now most common happen to experienced, certified people - people very much like the majority of Melbourne's diving community.

The dive itself is not more dangerous than it used to be. The question is whether the person doing the diving is adequately prepared for what the water asks of the body. Winter is the time to make sure the answer is yes.