FACT OF THE DAY

How to Read a Decompression Timer Dial

Four rings, one minute hand and a table printed on the dial: the logic behind a display dive computers retired, and why Ocean Crawler still builds one.

Image: Ocean Crawler Watch Co.

A decompression timer dial is, in Ocean Crawler’s words, “a specially designed watch dial with concentric circles representing depth and time readings.” The Rochester, New York microbrand walked through how it works in a September 23, 2026 guide bylined Christian Champion, and its own Decompression Timer puts the idea on the wrist.

Each ring stands for a maximum depth. On Ocean Crawler’s watch, a scale at 12 o’clock lists four bands: 25, 30, 35 and 40 meters on the left, with 85, 100, 115 and 135 feet on the right. The diver picks the ring that matches the deepest point of the planned dive. Numbers around that ring mark elapsed dive time, and the figures beside them give the length of the stop needed before surfacing, made at a shallow depth, typically 3 to 5 meters.

“The system depends totally on the minute hand of the watch,” the guide says. Ocean Crawler’s instructions have the diver start with the minute hand at 12, then watch where it falls on the chosen ring. On the innermost ring, covering 25 to 29 meters, no stop is called for until 34 minutes; a dive of 35 to 40 minutes calls for a five-minute stop, and 41 to 50 minutes calls for twenty. Only then does the bezel come in. The diver turns it so the numeral for the stop length (20 for a 20-minute stop) sits at the minute hand, and surfaces when the hand reaches the luminous zero marker.

The color-coded look the guide describes is older than Ocean Crawler. Mido’s Ocean Star Decompression Timer of 1961 marked its depth bands in yellow for 25 to 29 meters, green for 30 to 34, pink for 35 to 39 and blue for 40 to 44. Paul Wessel’s US patent 3,475,902 for a “Diver’s watch,” filed in 1968 and granted in 1969, works on the same principle, down to a stop “at a depth of 3 meters during 5 minutes.” Ocean Crawler’s own dial swaps the rainbow for orange and cream rings.

One caveat, stated plainly: a dial like this is a fixed table. It cannot account for repetitive dives, ascent rate or breathing gas, and it is no substitute for a dive computer and proper training. Read it as a record of how diving used to be planned.

Why this watch, on this wrist?

Nobody straps on a Decompression Timer to plan a dive in 2026. It earns its place because it keeps a working tool legible: a dive table printed on the dial, from an era when the watch was the dive computer. At $1,099, in runs of 100 per color with a Sellita inside, it is one of the more attainable ways to wear that idea, on a wrist that knows how to read it.

Sources: Ocean Crawler guide · Ocean Crawler Decompression Timer · Swatch Group (Mido) · US3475902A

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