Night dive at Gành Dầu

Eight metres. Forty minutes. Stay on the guide line for the first ten minutes to settle the eyes. Then patrol left, parallel to the reef, for fifteen minutes. Turn at the second mooring block. Patrol back. Exit at the same line we came in on.

Torch in the right hand. Backup torch clipped to the chest D-ring. Light signals only. A slow circle for OK. A side-to-side sweep for attention. A point and hold for follow my beam.

The brief from Mr. Huy was specific in a way day briefs are not. He said: at night, your panic is not a creature. Your panic is a feeling that arrives because you cannot see, and then you start filling in the dark with things you remember from movies. He said the cure is the torch and the line. The torch is the part of the reef that is real. The line is the way home. Everything outside the cone is a story you are telling yourself.

The descent was five metres of black water. The torch went on at one metre and the reef came up out of the dark a piece at a time.

The first ten minutes were calm. The cone of the torch made a moving circle of reef. Whatever was lit was the reef. Whatever was unlit was a colour I could not name. The trick was to keep looking at the lit part and not to keep flicking the cone outward to check the dark.

I did not entirely manage this. About fifteen minutes in, on the patrol leg, the cone caught the outline of something large at the edge of the visibility. I lifted the cone toward it. The cone did not reach. I held the beam steady in the direction of the thing for two seconds, and it did not come closer. It also did not go away. I lowered the cone back to the reef and kept moving on the patrol path.

Twenty-five minutes in, I felt the line again with my left hand, more often than the dive needed me to. Just to know the line was there.

We turned at the mooring block. We came back. We surfaced beside the same buoy we had used as a reference point. Forty minutes flat. No deviation.

The slip was the cone flick at fifteen minutes. The thing at the edge of the visibility was almost certainly nothing. Mr. Huy afterward thought it was probably a turtle. It could have been a fish, or a coral head with an outline that looked alive, or the way my own bubbles curved in the half moon. The slip is not that I looked. The slip is that I lifted the cone toward it. I broke the patrol of the reef to investigate a shape I had no information about, and in doing that I would have lost the reef for the duration of the look.

The cure was already in the briefing. The torch is the part of the reef that is real. Everything outside the cone is a story I am telling myself.

I am writing the slip because the next time the cone catches a shape in the dark and I lift the cone, I will be doing it on purpose, and I will have decided in advance whether it is worth losing the reef for. Right now I lifted the cone on instinct, and the instinct had nothing to do with the dive.

The night dive is what panic looks like when it is rehearsed instead of avoided. The pressure of not being able to see is identical to the pressure of not being able to predict, and the cure is the same. You do not look harder into the dark. You stay inside the cone of what is real. You hold the line.

The line, in night diving, is the procedure. It is a piece of rope. It is not interesting. It does not give you information. It is the thing that is there when the information runs out.