Yes, that might be mincing words but also another interesting story for next time.Įnjoy your diver’s watch, both on land and underwater: it’s much more versatile than you may think. There was no diving with compressed air in World War II! So it was technically not a diver’s watch but a water-resistant mission timer. But they were not used to measure dive time, only mission time. Regarding the first Panerai diving watches: they were actually Rolex movements housed in Panerai depth gauge cases. There is much more to it than that, but that’s also a story for another time. The Blancpain Fifty Fathoms and Rolex Submariner both came out in 1953, but only the Fifty Fathoms had a unidirectional bezel and could safely be used for diving with compressed air. I have two favorite dive watch bezels: the sapphire crystal bezel of the Blancpain Fifty Fathoms for its beauty and the ceramic bezel of Glashütte Original’s SeaQ for its retro look.īlancpain Fifty Fathoms Automatic of 2020 I promise that by the time the aircraft touches down you will have the new setup of your (now) double-time-zone watch ingrained in your brain. On your next trip, once you have buckled in and listened attentively to the safety lecture, say to yourself, “West is best, east is least.” And then set the bezel accordingly (yes, on a diver’s watch you have to set “the best” counterclockwise!) Changing that perception is a piece of cake. This might seem complicated if you’re just reading the description, but that’s only because as watch aficionados we’re so used to the hand position in relation to 12 o’clock. So I set the reference marker back four hours (to 8 o’clock), putting the local time on my virtual second time zone function to 4:11. Your watch can work for you so much more on vacation: like this Tutima M2 Pioneer (photo courtesy Sadry Ghacir)Įxample II: to dive in the Maldives for me means flying east (is least). The attentive reader may have already realized that in measuring decompression time the counterclockwise motion of the bezel is counterproductive: accidentally moving the bezel will lengthen the time, which might bring the diver to the surface too early. This scale is for timing decompression stops because most stops for the average sports diver are in the 15-minute range. Looking at the bezels of serious diving watches, we note they have minutes marked between 0-60 and 15. You’re in the shallows, your brain works again, and you count down five minutes. So when you reach three meters, you turn the bezel counterclockwise until the reference marker is at the minute hand and check for five minutes. And it is always a good idea to finish each dive with a safety stop of five minutes at three meters. The dive time from the bottom to the surface is already considered decompression time. One more aspect of using the watch as a no-decompression dive timer: the dive time starts at the surface but finishes in the depths when beginning the ascent. All calculations have been done and checked before the dive. This way, divers only have to keep the marker in mind and no confusing numbers. At which point, the diver must begin ascent. To set up the watch, experienced divers subtract 36 from 60, setting the minute hand to 24, which now counts down 36 dive minutes until it reaches the 60-minute mark. The no-decompression time is 36 minutes according to the 90s rule, which would call for a twin ten-liter tank of air. Now, let’s say the bottom of the wreck is at 27 meters. Experienced divers know that if something can happen, something will happen. They also calculate the necessary air supply and whether it will be enough for that dive, including a safety margin of one-third more. Setting dive bottom time using the bezel’s reference marker I’ll follow up on really deep diving with a mechanical watch in a future article. That’s 40 minutes of no-decompression time at 25 meters.Īt 30 meters it’s 30 minutes, at 40 meters 10, and unfortunately at 50 meters the formula no longer works, necessitating tables. Here is an example using a maximum depth of 25 meters: doubled makes 50, subtracted from 90 gives you 40. If you double the maximum depth and subtract the result from 90 you get your no-decompression time. But decompression tables were quickly developed to check no-decompression time – the time when a diver should resurface without having to make a decompression stop under water.Įxperienced divers (especially those who weren’t too excited about all these numbers) devised an easy rule to calculate decompression time in the head: the 90s rule. In the early 1950s there was no instrument available to calculate decompression times. Setting dive time using the bezel’s reference markerīut how does the diver know when to end the dive?
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