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Try this for size. Linear Point Intersect is a superb way of recording substrate type. When I had the chance to do a bit of this, we were using a 5m line with 26 points (20cm apart) on it. The points are sewn on fishing weights. The score card is an A4 slate with about 20-30 rows, 26 columns. Each row corresponds to a substrate type. You lay the line according to pre-declared rules (in our case isobaric, parallel to the main transect, etc, etc), and then swim over it; whatever is *directly* below each point is scored in it's appropriate box. Often you get runs, so count 1, 2, 3, 4, 5, shelly debris, 1, 2, 3, massive coral, etc. Sometimes you get 1, this, 1 that, 1 the other. The time it takes to do this task (just the scoring) varies a lot with depth. We spent five weeks doing these at 2m, 10m and 20m, and then a few days at a range of depths from 30m up. It was seeing the difference in time to do the range of LPIs that was noteworthy... times approximately; 5m 90" 15 3' 30 5' The other good narcosis test I know is cuttlefish tennis (or squat lobster if that's all that's around that day. I played myself once at **m on air and it was superb! My hands never missed, but my eyes were always looking at the wrong hand, the empty one. Hardly ever saw the cuttlefish. I was boxed, my whole body sort of throbbed. Very nice relaxed dive. Don't fancy going a lot deeper... luf and kisses Jason
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