light vessel automatic

In the middle of last week, the weather turned mild and sunny, so this weekend I did another two scuba dives. This time they were proper dives – down to six metres, which is not very deep, but deep enough that you have to go down slowly and allow your ears to adjust to prevent them from bursting. Due to some sort of blockage inside my head – probably the remnant of a bad cold last weekend – I had big problems adjusting the pressure in my ears, so it took me a long time to get down to the bottom. The problem with my ears made me very aware of the pressure differences (for the scientifically-inclined, at six metres down the pressure is 1.6 atmospheres): when you scuba-dive, you’re breathing compressed air that comes out of the tank at whatever pressure the water, and consequently you, are at, so if you go up too fast, then the air inside you is suddenly at higher pressure than the air or water around you. From six meters, that would make your ears hurt very badly. From deeper, worse things would happen. I was thinking about pressure when N-san, the diving instructor, pointed out a small, delicate, multicoloured creature called a ‘sea cow’ (in Japanese) on a rock. It looks a little like a slug, but a rainbow-coloured one, with lots of feathery little fronds coming off it. I thought to myself how strange it is that this delicate-looking little thing is actually at high pressure, and how if you took it up to the surface it would EXPLODE, and then I remembered that actually we were only six metres down, and not at the bottom of some ridiculous ocean trench, and that actually things at six metres down are not at such high pressure that they would do anything like exploding if you carried them up to the surface*. Still, when I went back up to the surface, I once again had trouble adjusting ear-pressure, and so had to go up slowly (maybe four or five minutes to cover six metres), and this time I realised that when you scuba-dive, you actually do become a creature of the deep: that even though you can see the surface up there – the place you’re from – you can’t just go straight back there, because the conditions there – the conditions that for 99.9% of the time support your life – would hurt you. It seems natural that going to an alien world should take time, that you should need to adjust, but it’s a strange feeling that the return must also take time, not because of the distance you have to cover, but rather because of what you’ve become in the meantime…

* Actually, now I think about it more scientifically, the sea-cow would also be much less affected by changes in depth than a diver, because of the crucial difference that the diver has a lung-and-headful of compressed air, whereas the sea-cow doesn’t. Since water isn’t really compressible, but air is, changes in depth will affect a diver much more than a fish. This doesn’t mean, though, that a fish brought up from enormous depths very fast would not explode. It might do.

That’s me in the yellow, by the way. I’ve cropped the picture at shoulder-height partly because I have an anonymity policy, but mainly just out of fear that if you saw both my lithe, wetsuit-clad body and my manly face at the same time, it would prove too much for you and you might swoon and smack your forehead on the keyboard in front of you. That’s Emiko in the pink, and N-san is in the black.