In this chapter, Beth learns to scuba dive and makes her first dive with Ethan as her instructor. There is a fictitious character in this chapter, the Prime Minister of The Bahamas, Manfred Minnick. The real Prime Minister of The Bahamas is Hubert Minnis, and I mean no disrespect to him, despite the similarity in their last names. This chapter contains oral, anal, lesbian, interracial and public sex, group sex, including a triple and double penetration. There is no COVID-19 or STD's in this fantasy world. My thanks to JohnnyGalt for his editorial services. Any mistakes remain mine.
My Voyage of Discovery, Ch 6 - The Bahamas
After lunch, Lynn changed into a bathing suit and she and I went down to the gym for scuba lessons with Ethan Somerville. Jìngyi was there too, also in a suit.
"So these are my three students for diving lessons today. Three lovely ladies, all new members of the crew. I'm going to talk to you about some of the important safety issues while diving, then when we anchor, we'll put all three of you in the water to test out your equipment."
He stood behind an air tank with a vest attached to it, two hoses going to two different mouthpieces, and some sort of gauge.
"This here piece of equipment is a self-contained, underwater breathing apparatus, which is where the word SCUBA comes from. It is attached to a buoyancy compensator vest, or BC. The only other pieces of equipment you need to dive are fins and a mask. You don't need a weight belt because the vest has pockets for weights. When you go diving, you want to see what weight works best for you and memorize how much weight you need, because you'll change the weights in the vest to your weight when you use it. Start with eight and go up or down from there. We don't have enough space for individual vests, weight belts, etc., so we stock a selection and it's up to you to find what fits and use it.
"Now here, at sea level, we have one atmosphere of pressure pressing on our bodies, the weight of all the air sitting on top of us, going up into space. It's roughly equivalent to 30 pounds per square inch. Now the reason your body doesn't implode is because your lungs equalize the pressure on the inside and outside of your body by breathing. The pressure inside is equivalent to the pressure outside.
"When you go down in the water, you add the equivalent of an additional atmosphere of pressure for each 10 meters, or roughly 33 feet of water. This means thirty three feet down, you've now got sixty pounds per square inch of pressure. If I took a balloon down in the water, the balloon would be half the size at ten meters as it was above the water. The balloon gets compressed enough so the pressure of the air inside equals the pressure of the water outside. Your lungs are like a balloon. The scuba tanks helps you equalize the pressure. The gauge recognizes the pressure at whatever depth you're at and gives you enough air to equalize the pressure. This means, you use twice the air at 33 feet that you use at sea level, three times the air at 66 feet and four times the air at 99 feet."
"Boyle's Law, right?" Jìngyi said.
"Exactly, Boyle's law. The deeper you go, the more air you use because you need air at higher pressure to keep your lungs filled. The tanks we use, have 80 cubic feet of compressed air. Roughly speaking, you can breathe twice as long at sea level as you can at ten meters and three times as long as at twenty meters.
"Now, let's look at our balloon again. We took it down to thirty-three feet and it became half the size, so when we come up and the pressure reduces, it starts to expand again and when you reach the surface, it's now back at full size. But what if when we were at thirty-three feet, we gave the balloon more air under pressure so it was the same size as it was on the surface. What happens when we bring it up now?"
"It becomes twice the size, possibly explodes," I said.
"Exactly, it explodes. The same thing can happen to your lungs. You take a lung full of air at thirty-three feet and hold your breath and come to the surface, the alveoli in your lungs expand to twice the size and explode. This is called an embolism and this is the first thing you worry about when diving."
"I didn't know scuba diving could be so dangerous," Lynn said.
"Everything is dangerous if you don't do it properly," Ethan said. "Driving a car is dangerous if you drive on the wrong side of the road, don't stop at stop signs, text while driving. You learn to drive on the right side of the road, stop where you're supposed to and look out for the other idiots who aren't paying attention. Diving is no different. You follow the rules and you're safe. You don't and you die. So, how do you keep from suffering an embolism?"
"Blow out air as you come to the surface," Jìngyi said.
"Right. Don't hold your breath. In fact, just keep breathing through your hose. The gauge is automatically giving you the air pressure you need for the depth you're at. Keep a good steady rhythm with your breathing, you give out air at one pressure and take air in at whatever pressure you need. Closer to the surface you get less air, as you go deeper you get more. Now all diver's learn this and very few ever suffer an embolism. If they're unconscious they may not be breathing deeply enough to get the air out. Unfortunately the biggest relative change in pressure is within the first 33 feet of depth. Going from two atmospheres to one is a doubling the volume. From three to two is a 50 percent change. Four to three is a 33 percent change. Five to four is only 20 percent.
"Where this becomes an issue is where people are diving below where people are snorkeling. A snorkeler is holding his breath. He grabs air at the surface, he holds it in, swims down, his lungs shrink, he runs out of oxygen, he comes up and his lungs expand to where they were on the surface. He usually has to stay within ten or fifteen feet of the surface. But he might be able to get down to you at thirty feet if he sees you have scuba gear and thinks he can get more air off you. So, he'll swim down, grab a puff of air of the diver's spare air hose at twice the pressure he had at the surface, and goes back up, still holding his breath. His lungs expand to twice their normal size; pop goes the lung, another idiot dead. Someone does come down and grab air off your hose, grab his arm, don't let him swim back. Go back to the surface with him encouraging him to breathe like you are, keep him from hurting himself. That brings us to the second issue you need to pay attention to, the bends.
"Breathing air under pressure causes nitrogen bubbles to build up in the tissues of your body. These nitrogen bubbles also want to expand when you come up. If these bubbles are in and around your joints and they expand, it hurts like hell and can do damage to the joint. These bubbles need to outgas slowly to keep you from getting the bends. To allow them to do this, you want to come up from your deepest depth slowly."
"No faster than the bubbles you're blowing out," Jìngyi said.
"How do you know so much about this?" I asked.
"Lot's of science classes, plus I've been looking at YouTube videos when I decided to take scuba lessons."
"She has more time for YouTube because she's not fucking all the time," Ethan said.
"But I'm having more fun," I said.
"I won't argue that," Ethan laughed. "In addition to coming up as slow or slower than your bubbles; we also want to arrange for safety stops on the way up. If you're diving at 33 feet, you might have a brief safety stop at 10 feet. If you go diving to 60 or more feet, you might have a safety stop at 30 feet and another at 15. Having a safety stop means you can't use all your air at depth because you might need to stop for five minutes at thirty feet and three more minutes at fifteen, so you need to keep some air for your stops. Now those nitrogen gas bubbles are still working themselves out of your tissues ten, fifteen, twenty hours later depending on how much, and how deep you've been diving. You shouldn't fly for one day after diving as the reduced pressure at higher altitudes can give you the bends too. And the plane doesn't make safety stops."
"How do you know where and when to stop and for how long?" I asked.
"Well, we used to use dive tables. You'd plan a dive for say sixty feet. Let's say you can stay at sixty feet for twenty minutes, provided you're not a heavy breather. You wouldn't go deeper than sixty feet, even if you saw some shiny object below you which you just have to look at. Even if you only spent ten seconds at sixty and spent the rest at fifty or less, you'd assume you spent all twenty minutes at sixty as a safety precaution. You'd plan your safety stop for spending twenty minutes at sixty feet off the table. It gave you an extra measure of precaution. Another thing to keep in mind is diving has a cumulative affect. Your second and subsequent dives should always be shallower and shorter. Your deepest dive should be the first one, with successively shorter and shallower dives the rest of the day. The tables change depending on how long you've been out of the water and how much you might have outgassed.
"Nowadays, we have dive computers which constantly make adjustments based upon what you actually swim. It will tell you when and where to make a safety stop and for how long, even telling you when you need to leave based upon your air consumption. Remember too if you take equipment someone else was wearing on a dive, it's now counting his depths and times, not yours, so it may give you erroneous information. I'm a cautious guy. I still like to have a general idea of what I should be diving according to the tables in case my computer battery dies, especially if I'm diving alone. If you dive with a buddy, and stay together, you can use his dive computer a little for both of you, always remembering they might be using less air than you so it's best to start for the surface together as soon as your computer craps out. But if I know what my profile is based on tables, I can still dive like I did before we got dive computers."
"I like your plan," Lynn said. "Better safe than sorry, I say."
He pointed at the gear set up. "Now, this particular rig weighs about 35 pounds and could weigh more depending on the lead you add to the BC. It will not seem that heavy in the water. Normally, you don't want any air in the BC to help you get down. Even though your body is generally compensating for the extra pressure, your ears can have a little more trouble compensating for the pressure differential and you have to do what is called the val salva procedure to help clear them, especially if you have problems with air pressure on airplane flights. You close your mouth, pinch your nose and blow lightly without releasing air out of your nose or mouth. It forces air up the Eustachian tube into your ear to equalize pressure. When you reach a depth you're comfortable at, you can add air to the BC to help you maintain neutral buoyancy. You don't want to be accidentally drifting higher or sinking lower than planned.
"You'll work harder and use more air if you have to keep swimming down to maintain depth and may go below your planned safe depth if you sink. The BC also uses air from your tank to add air to it with this little gizmo on the front of the vest. Now let's say you have a little air in your BC and you start up. Like your lungs, your BC will also expand and want to carry you to the surface faster than you should rise. Before coming up, let the air out of the BC so you swim up and your BC won't explode either. It does have a safety release valve, but don't depend on it. When you reach the surface you can put enough air into the BC to use as a flotation device so you don't tire yourself out waiting for pick up.
