What is the mammalian dive reflex?
The mammalian diving response, or "dive reflex," is the way our body automatically prioritizes blood delivery to the brain and heart when we hold our breath underwater. When your head is underwater, you are using up the oxygen in your blood and not replacing it by breathing, a condition known as hypoxia. The brain and the heart are exceptionally sensitive to hypoxia, whereas other parts of our body, such as our arms and our legs, can tolerate hypoxia much more easily.
Ingrid Eftedal, Ph.D.: Diving is associated with environmental factors that affect the cardiovascular system, and as long as the total amount of physiological stress is limited and the diver is reasonably fit, no data indicate that diving is harmful to the cardiovascular system. In addition to the health-promoting effects of exercise, one may speculate that diving could have additional benefits for the heart. It has been known for some time that breathing high amounts of oxygen activates an important type of proteins known as molecular chaperones (for historical reasons they are sometimes called heat shock proteins). Some of these molecular chaperones directly protect the heart from injury; extra oxygen is sometimes administered to patients before heart surgery for this reason.
Dawn Kernagis, Ph.D.: Scuba diving can be a fantastic way to burn calories, with a recreational dive burning an estimated 300 to 600 calories per hour depending on temperature and activity level. Although most recreational diving can be very relaxing while still involving increased activity and low levels of joint stress, which is beneficial to individual health, some forms of diving can be strenuous and could put an individual with predisposing conditions at potential risk of injury or incident. It's important to remember that physical fitness is a major factor in determining potential risk with any form of increased physical activity, so risk associated with increased activity will largely depend on a diver's overall physical condition.
Stingray stings are very rarely fatal. In fact, there have been fewer than 30 stingray-related fatalities that have ever been recorded! The few fatal stings are generally the result of the barb piercing someone’s heart, as happened with Steve Irwin, or as a result of the puncture wound getting infected.
Here are 20 common scuba diving hand signals. This guide is not intended as a comprehensive dictionary to all scuba diving hand signals, but simply an overview of some of the most commonly used underwater hand signs. You will notice that I have purposefully omitted hand signals to communicate tank pressure. I have omitted these signals because divers use such a variety of signals to communicate tank pressure that to state a "standard" signal would be more confusing than helpful. Be sure to review how you will communicate tank pressure with you dive buddies before your dives.
Fish Toxins that can make us very ill! v/r rick
This was a freak accident, but preventable. No flag and at least the article does not mention her dive buddy. v/r r2
PS If you are planning to go out anywhere during this week's Sportsman Lobster Hunt please be extremely careful. Over the past few years there are usually 1-2 divers that perish trying to get a few crustaceans. v/r r2
Not sure what happened here other than a vibrant young lady died while diving in 34' of water. This is insane, but lack of experience, panic, medical issue, etc along with a scuba instructor that lost sight of his student played into this tragedy. v/r rick