Sheck’s dive plan for his 1989 dive to 881ft

Nacimiento del Rio Mante in Mexico

Analysis and graphs generated by the CDM18 Dive Profile Analyser

Sheck’s ‘Dr-X’ Dive Plan

(converted from feet to meters. Analysis and graphs from the CDM18 Dive Profile Analyzer)

Run-time	Depth(m)	Ceiling(m)	Ascent Lim(m)	DCS-RISK	%-Oxygen	%-Helium
1	20	0.00	0.00		21	0
7	80	59.33	20.67		10	50
10	90	68.39	21.61		10	50
13	150	119.67	30.33		7	66
19	200	174.03	25.97		7	66
23	260	226.51	33.49		7	66
24	224	213.01	10.99		7	66
25	200	195.38	4.62		7	66
26	165	174.81	-9.81	DCS-RISK	7	66
27	150	163.38	-13.38	DCS-RISK	7	66
28	147	153.32	-6.32	DCS-RISK	10	50
29	144	147.90	-3.90	DCS-RISK	10	50
30	141	142.83	-1.83	DCS-RISK	10	50
31	138	138.06	-0.06	DCS-RISK	10	50
32	135	133.56	1.44		10	50
33	132	129.82	2.18		10	50
34	129	126.98	2.02		10	50
36	126	121.59	4.41		10	50
38	123	116.69	6.31		10	50
40	119	112.02	6.98		10	50
42	116	108.99	7.01		10	50
50	113	99.59	13.41		10	50
53	110	96.70	13.30		10	50
56	107	94.43	12.57		10	50
59	104	92.64	11.36		10	50
63	101	90.15	10.85		10	50
65	98	88.83	9.17		10	50
66	95	88.10	6.90		10	50
67	92	87.27	4.73		10	50
68	89	86.27	2.73	ICD-RISK	12	40
75	85	81.37	3.63		12	40
80	82	78.12	3.88		12	40
84	78	75.45	2.55		12	40
87	75	73.41	1.59		12	40
91	72	70.47	1.53	ICD-RISK	21	0
95	69	68.15	0.85		21	0
100	66	65.28	0.72		21	0
120	63	57.24	5.76		21	0
130	60	54.29	5.71		21	0
135	57	52.80	4.20		21	0
140	54	51.24	2.76		21	0
150	51	48.77	2.23		21	0
172	48	44.63	3.37		21	0
180	45	43.20	1.80		21	0
189	42	41.05	0.95		30	0
200	39	38.75	0.25		30	0
214	36	36.37	-0.37	DCS-RISK	30	0
231	33	33.88	-0.88	DCS-RISK	30	0
249	30	31.62	-1.62	DCS-RISK	30	0
270	27	29.03	-2.03	DCS-RISK	30	0
293	24	25.96	-1.96	DCS-RISK	40	0
322	21	22.76	-1.76	DCS-RISK	40	0
362	18	18.77	-0.77	DCS-RISK	40	0
405	15	15.54	-0.54	DCS-RISK	50	0
463	12	12.43	-0.43	DCS-RISK	60	0
537	9	8.56	0.44		70	0
650	6	4.77	1.23		80	0
802	3	1.33	1.67		100	0
850	0	0.58	-0.58	DCS-RISK	100	0

Sheck’s Isobaric Counter-diffusion Avoidance technique.

Or… See how a very clever man avoided in an in water DCS hit by gradual gas switching.

Notes from CDM Analysis results:

1. The dive profile is not bad at all, even by modern analysis standards
2. Two ICD events are predicted at 89 and 72 meters

“At 260 feet and 250 feet… (80meters)

I counted sixty-second stops with my fingers, then addressed a new source of concern: Jochen and Gene’s mysterious vestibular hit. At 240 feet I had to switch from breathing 50 percent helium and 40 percent nitrogen to air, which contains 79 percent nitrogen. According to their information, the abrupt increase in nitrogen could result in instant death. And all authorities predicted a sudden onset of severe narcosis.

To make the switch as gradual as possible, I took only a single breath of air from the tank we had earlier left at 240 feet, then switched back to the helium mix for two breaths. Then came two air breaths, then back to the deep mix for one inhalation. Finally I switched over to air completely, bracing myself for the severe narcosis and dreaded vestibular hit, all the while doing my best to count off the seconds required for the stop. Nothing happened, no narcosis, no sudden lapse into unconsciousness. The only thing I felt was warmer, thanks to not having to breathe helium any more.

Apparently my strategy of keeping a maximum amount of nitrogen in the deep mix worked.”

Sheck Exley Mexico Dive

Sheck’s dive plan for his 1989 dive to 881ft

Nacimiento del Rio Mante in Mexico

Sheck’s ‘Dr-X’ Dive Plan

Sheck’s Isobaric Counter-diffusion Avoidance technique.