The top dive sites that demand extra caution

Diving into some of the world’s most popular underwater destinations can be exhilarating, but these sites are also known for their unique dangers. That’s where DAN (Divers Alert Network) comes in. DAN is an organization dedicated to diver safety, offering assistance to divers worldwide and collecting critical data on diving-related incidents. Their data forms the backbone of a recent report, highlighting six of the most popular dive spots that demand extra caution. By analyzing calls for help received by the DAN Europe alarm center, they identified sites like Egypt’s Blue Hole and the wreck of the SS Thistlegorm as hot spots for diving accidents, often due to a mix of environmental hazards and human error. Their report, very worth reading, summarizes the specific dangers for each location.

Blue Hole (Dahab, Egypt)

Depth and Disorientation: The Blue Hole reaches depths beyond 120 meters, and divers can easily get disoriented or venture too deep, particularly when searching for the archway at 55 meters, which connects the Blue Hole to the open sea.
Narcosis and Skill Limits: Unskilled divers may exceed their training limits, leading to narcosis, which impairs judgment.
Freediving Risks: Freedivers often dive alone or without a safety team, increasing the risk of accidents. Stephen Keenan's fatal accident during a freediving project in the Blue Hole was impressively portrayed in the film “the deepest breath”. You can find the discussion here on dekoblog.
Dehydration and Competitions: Some divers get dehydrated or take on risky bets, further increasing danger. (This report is written on real life phone calls!)

SS Thistlegorm (Shaab Ali, Egypt)

Strong Currents and Poor Visibility: The dive site is known for strong underwater currents and variable visibility, making navigation challenging.
Square Profiles: The square dive profiles (extended bottom time with rapid ascent) increase the risk of decompression sickness.
Surface Hazards: Boats and platforms at the surface pose threats during ascents and descents, especially in rough seas.
Fatigue and Dehydration: The trip to the wreck is long and tiring, often starting very early in the morning, contributing to fatigue and dehydration, which can lead to decompression sickness. Combine this with unlimited diving the days before and you end up in the hyperbaric chamber.

MS Zenobia (Larnaca, Cyprus)

Too easy to dive: The MS Zenobia is a 170-meter-long wreck lying on its port side at depths between 17 and 42 meters. Its cargo of cars remains on board, making it an intriguing site for divers. The dive is relatively easy, making it suitable for open water divers exploring the exterior, and it is one of the most visited wrecks in the world.
Sharp Metal and Marine Stings: The wreck has sharp edges, and divers risk cuts or stings from marine life if they lack proper buoyancy control.
Disorientation: Due to the wreck’s large size and complex structure, inexperienced divers can easily get disoriented.
Failure to Monitor No Decompression Limits (NDL): Divers may fail to properly track their NDL, leading to potential safety issues.

Haven (Arenzano, Italy)

Depth and Disorientation: Diving at significant depths (up to 90 meters) increases risks, especially when divers lose orientation or ascend too quickly.
Equipment Failures: Pre-dive equipment checks are critical, but some divers neglect these checks, leading to hypoxia in CCR-divers or other emergencies.
Currents and Long Distances: Currents and the vast distance between points of interest on the wreck make planning and navigation crucial.

Lake Garda (Italy)

Extreme Depths: The lake features almost vertical underwater walls plunging to more than 200 meters, and divers may overestimate their ability to handle such depth.
Cold and Fatigue: Divers may not account for the cold, fatigue, or the impact of dense breathing gases at depth, which can impair performance and decision-making.
Dehydration and Poor Planning: Divers often neglect hydration or dive planning, making dives more dangerous.

El Hierro (Canary Islands, Spain)

Altitude Risks Post-Dive: The main hazard here is ascending to altitude after diving, as many accommodations are located at high elevations. This significantly increases the risk of decompression sickness.

It's not the dive - it's the way of diving which makes it the danger.

These dive sites are not particularly dangerous. The main reason they appear on this list is that they are very frequented. The most important measures for preventing diving accidents (on any dive) can be distilled from the consultations:

1. Stay within your skill level: CMAS-trained divers are sick of hearing this saying. But it's true. Only dive to depths that match your training and experience. Avoid venturing into areas or conditions (like wreck penetrations or deep dives) beyond your certification.

2. Use proper equipment and check it thoroughly: Always inspect your gear before diving, especially on technical or deep dives. For wrecks, ensure you have appropriate equipment such as dive computers, Nitrox, and redundancy for technical dives.

3. Plan your dive and dive your plan: Meticulous dive planning is crucial, particularly at sites with strong currents, complex wrecks, or deep profiles. Stick to the plan to avoid disorientation or exceeding your limits.

4. Use mooring lines for ascents/descents: These lines help you control your buoyancy and maintain orientation in strong currents or deep dives. Always use them to avoid drifting or rapid ascents.

5. Hydrate and rest properly: Dehydration is a major risk factor for decompression sickness (DCS). Start hydrating the day before your dive, and ensure you’re well-rested to handle the physical demands of the dive.

6. Listen to local guides: Rely on the expertise of local dive professionals who are familiar with the site’s conditions. Follow their advice closely, as they know the potential hazards and best practices for each dive site.

7. Avoid altitude after diving: If you’re diving in areas like El Hierro, avoid ascending to high elevations (such as hilltop accommodations) to early to prevent decompression sickness.

Personal comments:

When I asked a diver after a consultation due to a decompression incident what his next diving plans were, he replied that he wanted to dive the “Haven” - with compressed air...(!). So much for the effect of my advice. Hopefully the rigorous safety measures and controls in place there will do more to prevent another incident than my medical expertise.
No doubt: Hydration is important and prevents decompression incidents. However, the recommendation often made, including in this DAN report, to avoid coffee and other caffeinated drinks is no longer up to date. It is better to drink a coke, for example, than to hydrate too little or not at all and coffee won’t dehydrate you.
How it is possible to suffer hypoxia on descent after an adequate CCR-predive-check is beyond my imagination. The keyword here is probably “adequate check”. A checklist should always be completed before a CCR dive. This is also the recommendation of the last rebreather forum (RF4).
It is interesting that El Hierro appears on the list and the explanation why. In fact, on this island you can find accommodation at altitudes of around 1000 meters - which advertise with pictures of divers! This example shows that the risk of decompression sickness is greatest AFTER the dive, because it is then when supersaturation reaches its maximum, and reminds us that flying is not the only concern when it comes to travelling after diving. If you have to ascend to altitude after a dive, it is essential to wait long enough before ascending. Tables for this issue exist. Nitrox is highly recommended for such dives. It is said that decompression incidents have happened on the San Bernardino after a diving weekend on the “Haven”...