Several years ago, my girlfriend and I got our Open Water Scuba certification. We haven't used it, regrettably, but thinking about it today inspired some thoughts.
In some ways Scuba diving is like zazen. For one thing you have to remember to breathe. In both, breathing normally will make you relax and more comfortable. When Scuba diving, breathing is very important since the volume of air in your lungs will make them expand like balloons as you ascend since the pressure decreases. The worst that can happen if you forget to breathe in zazen is lightheadedness and maybe loss of consciousness.
You also practice in a controlled setting like a pool before being let loose in the wild. Sitting in the controlled setting of a cushion prepares us for what awaits us in the world.
Most people who haven't Scuba dived don't appreciate the beauty of what you're actually doing when you suit up. You are basically strapping a submarine to yourself, but it's more than that. In a normal submarine, you're just a passenger, even if you manipulate the controls, physically you're just a passenger. When you put on your tank, regulator, and buoyancy control device/vest (BC, that vest thing you wear) you are becoming a cyborg.
I don't mean in some romantic sci-fi way, but in a technical way as a mixture of organic and technological. In a submarine, you have levers and switches to control depth by flooding and evacuating ballast tanks. When you Scuba dive, the BC is the primary ballast tank, but your lungs are full of air as well. Anyone that's ever sat in water that covered their chest has experienced this; you breathe in and you float up, exhale and you sink.
When you dive you aim for neutral buoyancy, neither sinking nor floating. (hey, look! a middle way) Because the volume of a mass of air decreases with the added pressure of progressive depths, you can't just set your buoyancy at the top and leave it, it requires constant adjustments. When you're in forty feet of water and not on the bottom, unknowingly doing either is pretty easy and can cause big safety issues. When you're swimming along the bottom, it can make diving unpleasant for you and everyone around since bumping or brushing a muddy or sandy bottom will stir up visually impenetrable clouds. For people with large lung capacities, this can be such an issue that a special Precision Buoyancy certification class is offered.
I experienced this first hand and thought I had it under control. When we were in the pool at the dive center, we were made aware of the effect breathing had on our buoyancy and were told how we can use it to make fine adjustments without adding or letting air out of our BC. Inhale a deeper breath than you exhale, you'll go up a bit. Exhale more than you inhale and down you go.
Unfortunately when we got out in the real water, the excitement of the situation overran my control. In the muddy water of the lake, you could barely see ten feet in front of you and make out detail at about five. Being neutrally buoyant is like being weightless, you can't feel which direction gravity is pulling you. (why they use Scuba diving to train astronauts for space walks) When you don't have a horizon, bottom, or surface as references all you see around you is a brown void of muddy water. Other than your depth gauge you have no way to tell where you are.
In my excitement, I lost control of my breath-based buoyancy and it caused frustration that distracted me from the wonder of the experience.
This leads me into what really inspired this connection. I had been sitting for twenty minutes everyday but I've been pushing for thirty so the difference in time between what I sit at home and at the Zen Center isn't so great. I had to work my way up to twenty minutes just as everyone should; sitting silently and still with yourself for that long is difficult without experience and discipline. Telling my teacher this, she urged me towards the thirty minutes putting into words some of the observations I'd made. Sitting for twenty minutes is just enough time for the mind to calm down, to get any sort of real benefit those extra ten minutes are needed. It's like putting a baby down for nap, letting them cry themselves to sleep only to get them up just as they pass out.
In the case of my Scuba example above, I didn't have enough time to get comfortable in my new and strange "body" to calm down enough to enjoy the environment it allowed me to exist in. As soon as I was beginning to, it was time to get out.
Usually when someone goes on a Scuba trip, there are several dives over the course of a few days. This would allow them to really get comfortable with their bodies and the environment so that after the first couple dives they would just slip into the experience as if it were natural.
I've heard when someone goes on a Zen retreat, after the first couple sessions, calming the mind becomes easier each time you sit. I could see how this is probable for the above reason.
When I sit in the morning, my mind isn't really awake yet so it hasn't had time to fill up with the days thoughts and worries. At the end of the day it's harder for me to sit since my head is full of all that stuff. On the other hand, sitting clears it all out for sleeping.
- Scuba diving: fun outdoors in the sun with interesting people, visiting exotic places and seeing exotic creatures in their natural habitat, kind of expensive
- Zazen: sitting with yourself uncomfortably on a cushion staring at a wall experienced indoors in a dimly lit room where the wildlife outside is no more than an annoyance, it's free