Divers in romance (part 12) Review of using full face mask with buddy phone潛水員的浪漫（十二）測試全面罩面鏡及水底通訊器

Testing buddy Phone

We bought a pair of OTS Guardian full face mask and buddy phone D2.

The buddy phones can communicate between 50 to 500 meters, which depends on the sea conditions and noise levels. The sound is digitised and transmitted through ultrasound using upper single sideband. This buddy phone operates by a 9V Alkaline battery. It 

Buddy Phone D2

Wearing a FFM with a buddy phone

is quite easy to install by following the instructions of its manual. The design of the Guardian full face mask is fantastic. 
1. The regulator is very easy to lock and unlock with the FFM.
2. It makes use of the tank air that is dry to blow the screen of FFM before we breath. This function prevents fogging effectively.
3. As the mask always has positive pressure inside, water is not possible to seep into the mask that occurs quite often on traditional masks. 

The below video recorded our communication underwater, which was extremely clear, but it has a drawback that makes us consume much more air than usual, especially when we speak.

For safety, the diver who uses FFM needs to bring a spare mask and learn mask removal and replacement. Removal and replacement of traditional mask is like riding a bike, but it is difference from doing on FFM. 

FFM is integrated mask and regulator, so you lose your sight and breath when you have removed it. You need to do both regulator and mask clearing at the same time. This is the reason why I said the actress who is in the film 47 meters down must be filmed on land.

Common scuba Myths

Once in an underwater conversation, she said she felt shiver, because she was during the period of menstruation. Then she asked whether she would have hypothermia.

Heat lost

I remembered I watched a programme of "Troubled Waters", which was on the show of Dataline NBC of Australia. They interviewed a couple who floated 19 hours overnight when they and their dive boat did not connect after a dive on the Great Barrier Reef. In the programme, they mentioned they experienced signs of hypothermia, as many people do not understand shivering and teeth chattering does not mean you have hypothermia. They think hypothermia and chilling are the same thing, but they are not. Hypothermia is defined as a core body temperature of less than 35 degree Celsius.

diving boat

The second myth is that they did not do any exercise to keep the heat in their core organs, because they thought blood would be sent to the muscles when doing exercises. The truth is that it is not always the case the exercise in the cold must only make you colder. Doing exercise in cold water can generate enough heat to match or surpass the larger thermal drain, depending on water temperature, work load, duration

of exposure, your body composition, and what you are wearing. It is true that exercise increases heat loss, but it is an important point that it does not mean that you will always cool. It depends how much heat you keep and how much you lose. If you generated more heat than you lost, you would be warmer than nothing to do.

The third myth is blood of menstruation will be as a shark bait that I mentioned in the previous chapter. 
According to a diver researcher who is Dr. Carl Edmonds found that Australia’s shark attack tracking system reported nine times more shark attacks on men, even though there was an even number of male and female swimmers.

Menstrual blood does not attract sharks. Neither does menstrual blood attract grizzly bears during camping trips, cause wine to sour as stated in ancient religious writings. As we saw in many sharks watching dives, they dropped a large amount of blood and dead fishes to attract sharks. How much of menstrual blood seeps from uterus in a dive? It had been difficult to measure before Camilla has used menstrual cup because of reducing the usage of disposal materials.

Using a menstrual cup needs more care of being infected and leakage than pads. It needs to be sterilised before it is inserted into the vagina. I have learned how its usage is. Firstly, I fold it into a small size and insert into her vagina. When I release it, the cup reinstates to its original cup shape and creates a seal to save her from any leaks. After that, I  need to check whether it has opened and sealed properly by circling my finger around the base of the cup. The manufactures advise that the cup should be cleaned at most every 12 hours. I notice that the menstrual blood has never filled more than half cup. It is much less than this amount for an hour dive and it is not discharged at the same time. So, it can't play a role as a shark bait.