Peter Benchley has given sharks a bad rep. He wrote the book Jaws and the movie portray a great white shark as a boogie animal hunting people. While it is true that there are shark attacks on people and that harm is not trivial. However, most sharks avoid humans. Other strategies to avoid getting bitten by a shark are:
- Avoid areas where the great white shark is plentiful such as off the coast of South Africa.
- Do not go swimming in waters that have poor visibility. Usually clear water becomes turbid after a rain storm. The streams and rivers that feed into the ocean carry more silt down to the ocean during rain storms. This makes it harder for the shark to visually see what is on the surface. The shark detects a person on the surface by vibrations in the water and the bioelectromagnetic field you emit. So the shark detects it but cannot tell if it is a seal or not. It comes up and takes a bite. Tasting neoprene of the swimmer/diver/surfboarder the shark lets you go. However, that “taste” is large enough that if it is a seal the seal cannot get away. A big bite, not a nibble.
- Leave marine life alone. Do not try to pet a shark. So not carry food such as dead fish, chum, et al.
A few years ago I did a drift dive near Moliki. We were hopefully going to see Hammerhead sharks. On board were a few people with rebreathers. Rebreathers allow a diver to breath underwater without giving off bubbles. Fish do not like all those bubbles. This is called a closed circuit system, The exhaled breath is passed through a canister of chemical that removes CO2. There is a small tank of O2 and it is injected into the inhaled breath in the proper ratio of O2 and Nitrogen. (about 20% O2 and 80% Nitrogen. You do not want to breath only O2 at or above 2 atmospheres of partial pressure. You run a great risk of central nervous system (CNS) issues such as passing out. For example, for every 33 feet you descend in water you are breathing from your scuba tank at 1 more atmosphere. Therefore, if you have a tank of only O2 at the surface you are breathing at 1 atmosphere. As you descend to 33 feet you will be breathing the O2 at a partial pressure of 2 atmospheres. (the partial pressure of Nitrogen in this case is 0 because there is no nitrogen in the mix in our example) Recreational divers use normal air when they dive. Yes, Dr. Dominic D’Agastino in Florida found putting the body into Ketosis seems to get around this partial pressure of O2 – I do not know the details and would not experiment. I stick well within with recreational diving limits. I recommend others do also)
In that dive we did not see any hammerheads. The rebreather people went off on their own and dove to the bottom at around `120 feet. A few years pass by and I am talking with a dive master about the trip. She said she knew the rebreather guys. (Most people do not have rebreathers; the equipment is very expensive and takes a lot of training. You do not just go from standard recreational scuba diving and then just put on a rebreather unit.) She said they go down there and fix equipment that a local college uses to study hammerheads. That while they are trying to fix things the hammerheads detect them by their bioelectromagnetic fields. Since there are no bubbles they investigate. She said they are like puppies “Hey whatcha doing? “and put their heads to see what is going on. So the divers have to push them away! LOL.
Chance Musings 