Divers Alert Network

From the first exploratory scuba dives on the SS Edmund Fitzgerald to expeditions at the bottom of Belize's Great Blue Hole, Terrence Tysall has spent more than four decades exploring some of the world's most remote underwater environments.

On this episode of The DANcast, the NAUI Worldwide Director of Training discusses deep cave systems, historic shipwreck exploration, scientific expeditions, and the mission of the Cambrian Foundation.

▶️ Watch the full episode: https://youtu.be/wPGgWQLEJwQ

The conversation also examines the importance of conservation and why thoughtful, comprehensive training remains one of the most important investments divers can make in their safety underwater.

Terrence Tysall, NAUI Worldwide | Training Terrence Tysall has spent more than four decades exploring some of ...

A dive trip filled with unforgettable wildlife sightings took an unexpected turn when diver Mary McCombie suffered a severe facial injury in Magdalena Bay.

While snorkeling during a baitball encounter, striped bonitos bit through her lower lip and into her chin.

Through coordination between the liveaboard crew, Los Cabos medical providers, and DAN, Mary received evacuation assistance, urgent medical care, and reconstructive surgery.

"What I had hoped for and can now confirm is how good DAN insurance is and how well DAN partners with dive operators and medical facilities. I now have a nearly invisible pair of scars and one heck of a story."
— Mary McCombie, DAN Member

🐟🪡 Read her full story in Alert Diver magazine at dan.org/bitten-by-bonitos/.

“In the end, I want to tell a good story. I need the technical dive skills to do it safely, and I want to be visually creative to communicate differently.”

Throughout her career, Jill Heinerth has ventured into underwater environments few people will ever see. Driven by curiosity and supported by the preparation and technical skills such dives demand, she has spent decades in underwater caves and other remote environments, sharing discoveries made along the way.

Through photography, film, and writing, Heinerth brings audiences into these hidden places, illuminating the science, conservation, and human stories beneath the surface.

Revisit this 2020 Alert Diver profile of Jill Heinerth: dan.org/shooter-jill-heinerth/

📷 Jill Heinerth
✍️ Stephen Frink

Decompression stress begins to take shape long before the descent. While divers often focus on depth and bottom time, pre-dive physical states also influence decompression outcomes.

Everyday factors such as sleep, illness, hydration, exercise, and alcohol consumption can interact with decompression physiology. When sources of physical stress are present, especially when multiple stressors occur at the same time, the cumulative effects may reduce a diver's physiological reserve and potentially narrow safety margins.

Part 1 of this new Alert Diver series, A Timeline of Decompression Stress, covers how the physiological conditions you bring to a dive can influence decompression stress and dive safety.

Read the article at DAN.org/a-timeline-of-decompression-stress.

✍️ Matias Nochetto, MD, and JoAnn Perry

When Thomas Powell witnessed two separate dive incidents involving instructors nearly a decade apart, he noted a common factor: both divers' symptoms improved after pressure from their drysuit neck seals was relieved.

This Alert Diver Incident Insight examines how excessive pressure from an improperly fitted neck seal may stimulate the carotid sinus reflex, a physiological response that can reduce heart rate and blood pressure and potentially contribute to dizziness, confusion, lightheadedness, vision changes, or loss of consciousness.

A properly fitted drysuit neck seal should keep water out without restricting breathing, swallowing, head movement, or circulation. If a seal feels tight or restrictive on land, it should be adjusted before diving.

Read the full article: DAN.org/check-your-neck-seal

✍️ Thomas Powell, PhD
📷 Jill Heinerth

(Note: Unexplained loss of consciousness or altered mental status always warrants medical evaluation, even if symptoms resolve quickly. Responders should not assume relieving a tight seal fully explains the event.)

Representatives of the United States NEDU Navy Experimental Diving Unit visited DAN Headquarters this week to discuss ongoing research collaboration in diving and hyperbaric medicine.

Learn more about NEDU’s pioneering work in this Alert Diver feature: dan.org/deep-in-the-science-of-diving/

Immersion Pulmonary Edema (IPE) occurs when fluid leaks from the bloodstream into the air sacs (alveoli) in the lungs during immersion, impairing normal gas exchange. 🫁

Symptoms may include the rapid onset of shortness of breath, coughing, respiratory distress, and, in some cases, blood-tinged or frothy sputum. While IPE can resemble drowning, the fluid originates within the body rather than from inhaled water.

Researchers believe IPE is multifactorial. During immersion, blood shifts from the extremities to the body’s core, increasing pressure within the pulmonary circulation. Combined with factors such as exercise, breathing resistance, denser breathing gas, and thermal stress, these changes may contribute to IPE.

Well-supported risk factors include age over 50, NSAID use before diving, physical exertion before or during a dive, increased work of breathing, tight-fitting suits or equipment, cold-water exposure, and arterial hypertension. Overhydration has also been proposed as a possible risk factor.

Because IPE can resemble other dive-related conditions, recognizing the signs and symptoms is essential. Even if symptoms improve after exiting the water, sudden shortness of breath, a persistent cough, or other breathing difficulties warrant medical evaluation.