16 April, 2000

Underwater Dangers 2

Question 57: What Antarctic bird closely resembles a bird we see in Alaska in the summer?

Continued from 4/15/00...

One of the reasons we dive with a buddy is to have someone to help us in case of an equipment failure. We are dependent on all of the delicate mechanisms, hoses, and connections between the tank and our gear and lungs. If the power inflator hose to the dry suit becomes disconnected, it impairs our ability to regulate our buoyancy. How serious a problem this is depends on when in the dive it occurs. It can be reconnected underwater by a buddy fairly easily. A more serious problem is ice formation in either the first- or second-stage of the regulator. Because of the valve designs, ice crystals tend to cause the valves to stay open and provide too much air rather than shutting off the flow of air completely. Diving in water that has gone to -1.8 degrees C, regulator ice formation is always a possibility. Once dry gear is immersed in saltwater there is little danger of ice formation. The problem generally starts at the surface where the regulators can come into contact with fresh water. Any fresh water that the regulator comes into contact with freezes at 0 degrees C. This can be condensation from our breath or snow meltwater sloshing around in the bottom of the boat. If the air temperature is below freezing, we try to avoid breathing in through the regulator second-stage until we have actually entered the water. On the way to the dive site, we are careful to keep the assembled SCUBA units out of any water on the floor of the boat.

We have had a few frozen second-stages so far. They have all been obvious at the surface as soon as the diver entered the water. Geyser-like air gushing up from your gear is difficult to miss! After a few minutes of soaking in sea water and tinkering, the ice gets dislodged and we are able to continue our dive.

Frozen open first-stage regulators are far more dangerous underwater. The free-flow of air into the drysuit and BC can inflate them faster than their dump valves can exhaust the air, leading to an uncontrolled ascent. Divers must always ascend slowly to allow the nitrogen dissolved in blood and tissues to outgas. If the rate of ascent is too swift, the pressure on the diver's body is reduced so quickly that the dissolved nitrogen comes out of solution and forms bubbles within the diver's body. This is what causes decompression sickness or the bends. The symptoms depend on where the bubbles form. Bubbles in the blood stream can block circulation, while bubbles in tissues distort and damage tissue as the bubbles expand. A diver can get "hit" in the skin, limbs, central nervous system, and pulmonary system. In severe cases, major injury or death could result.

The last "danger" is less immediately dangerous but has been our most common problem--holes in our dry gloves. If we are lucky, we find the hole within the first ten feet or so of our descent and are able to resurface, change the glove, and then do the dive. If it isn't noticed until the diver is at depth, the buddy team will have to decide whether to abort the dive and surface or continue with a shortened version of the dive. The cold water will not only flood the glove, freezing the diver's hand, but can continue down the diver's arm through the wrist tube meant to allow air from the suit into the glove during descent. With a painfully cold hand and compromised body heat, the diver is best off calling an end to the dive and surfacing at a safe pace once the problem is identified.

Answer 56: Seabirds such as albatrosses, petrels, prions, fulmars and shearwaters

have a salt-excreting gland that is visible on their bills. Look closely at the photo on March 17 of the young Giant Petrel.