amanico
[JLC Moderator]
342310
There is no more rationale, Melvyn. Great question, though...
Nowadays, there is no more rationale, since Computers have replaced wristwatches for diving activities, and for a long time, now.
Nowadays, there is no more rationale about watches in general, since our cell phones give us the Time and for free. 
Rationale goes, most often, against passion and pleasure.
BUT, in the end o the 50ies, when the DSA was issued, the idea was to offer the possibility to the diver to feel the alarm warning him that the diving time was over, with the vibration on his wrist.
Was it a good idea? Yes. Vulcain took this idea, 2 years after the DSA for its famous Cricket Nautical.
Was the DSA a model of a diving Watch? Certainly not, as the bezel was not turning, which would have offered two ways to read the elapsed time.
Best,
Nicolas
Tribute To Deep Sea Alarm US: Some summer pictures.
What is the rationale for this JLC Deep Sea Alarm watch?
There is no more rationale, Melvyn. Great question, though...
