He describes the current local free-diver spearfishing community in this way: “Small and kinda like a tribe.” This tribe has its own elders and governance in the form of the San Diego Free Divers; Sweeny is a board member. The club was founded in 1994, and some of the members are still active free divers in their 70s and 80s, even though the sea constantly reminds a diver of one’s place in the food chain.
“For example,” says Sweeny, “if you spear a fish, you’ve got about 15 minutes to get it into the boat before the sharks show up.” Sharks are drawn by the scent of blood in the water.
Has that ever happened to him?
“Yes,” Sweeny says over dinner at the Waterfront Bar & Grill in Little Italy. “I’ve gone through quite a few of my nine lives.” Before the evening is over, he invites me to go out on his boat.
“We have a saying,” says Michael Timm. “‘The scuba diver looks around the sea; the free diver looks inside himself.’ If you don’t have control over your mind, you won’t dive deep, and you won’t live very long.”
Timm owns Dive California, a scuba shop on Sports Arena Boulevard that dates back to 1953. He teaches both scuba and free diving, and he heads a Meetup group called “Total Immersion Divers,” which he thinks has between 40 and 50 members, more of them traditional scuba divers than free divers. At 49, he is tanned and fit, with remnants of a German accent.
“The urge to breathe?” Timm says. “We all get that. You have to overcome it. One thing we teach our students is to deal with the contractions.” He explains how one’s diaphragm contracts as the breath is running out. If it goes on long enough, contractions are followed by what appear to be the same experiences those who’ve had near-death encounters describe. “Some people see a black tunnel. Others see lights. But the contractions are super uncomfortable.” Overcoming them, Timm says, “is the difference between holding your breath for three minutes or for nine minutes.”
“It’s doable,” he says. “Yes. When I began free diving, I was fearful of holding my breath for 20 seconds. You have to practice.” Dry practice, that is, while lying on a bed or a couch. “You hold for three minutes, then take a three-minute break. This gets you used to carbon dioxide buildup.” Timm says he can now hold his breath for six minutes while lying on the water’s surface.
After a stint in the German navy, Timm shipped out to the Canary Islands. There, he fell in with some locals who were free-dive spearfishing. “I got hooked.” He came face-to-face with death when a dive buddy went down one day and never came up. “We found him in 60 feet of water. He still had a fish on his spear. He died for this stupid little fish.” It was Timm’s first encounter with shallow-water blackout.
Timm’s own free-diving limit is 125 feet, or about the height of a 12-story building. “Number one is this: if you can’t imagine doing it, then you can’t do it in real life. I visualize my dives, and I learned about that from a variety of other sources.” Tony Robbins, the life coach self-help guru, is invoked. “It’s a very powerful tool, to see your goal, and to get the clutter out of your mind, and to reduce your resting heart rate.”
Timm says that free diving is one of the fastest growing sports. “It’s the next step from snorkeling,” with this caveat: “Water is generally a scary element for a lot of people. I tell students to give it time. We lived in it for nine months. Give it time, and you’ll find your way back.”
“In my mind there’s only one real major risk associated with free diving: shallow-water blackout.”
Tom Neuman, MD, FACP, PhD, is an authority when it comes to dive physiology. His areas of expertise include undersea and hyperbaric medicine, pulmonary disease, and decompression sickness. He graduated from New York University and is co-author of Physiology and Medicine of Hyperbaric Oxygen Therapy. Neuman talks with his hands, sometimes with his entire upper body. He lives near the coast in Del Mar and is semi-retired. He is, as he puts it, “pushing 70.”
“Without going into a huge amount of detail,” he says, “[shallow-water blackout] is holding your breath until you pass out. Normally, you can’t do that. Ventilation is triggered by the amount of carbon dioxide in your blood. Human beings are relatively insensitive to low oxygen in our blood, compared to high carbon dioxide.” What limits the ability to hold one’s breath, Neuman says, is one’s tolerance to carbon dioxide. “The moment you start holding your breath, the amount of carbon dioxide in your blood starts to go up.”
In more scientific terms, it’s the physiological consequences of carbon dioxide buildup that trigger respiration. “The term for the change in pH [in the blood] due to elevated carbon dioxide is called ‘respiratory acidosis.’ You don’t really have a sensor in your body for carbon dioxide — you have a sensor for the pH of your blood. You feel short of breath. You want to breathe.”
Neuman says that the oxygen level in one’s blood doesn’t go down in any appreciable amount for the first minute to a minute and a half of breath-holding. “But go past that, and your oxygen level goes down to the point that you can lose consciousness.
“But let’s go back to what we said about your body’s sensitivity to oxygen and carbon dioxide. Your carbon dioxide level is still low because of previous hyperventilation. And you’re relatively insensitive to the amount of oxygen in your blood. At that point, you’re capable of passing out underwater.”
Shallow-water blackout comes on without warning. Paradoxically, a victim has no sensation of being out of breath. “If you look at the number of people that die diving for abalone each year…some deaths are shallow-water blackout, some of them get hung up in the kelp, and some of them are my age and happen to have the big one while they’re in the water.”