Deep Blue Daynight Mil T-100 review

Keith Campbell takes a look at the Deep Blue Daynight Mil T-100 – a chunky divers watch with lume to die for. So, what’s the verdict?

Deep Blue Daynight Mil T-100 Review

Founded in 2007, Deep Blue is a New York-based company but they source their parts from all over the world to create a very functional, no-nonsense range of professional dive watches. All the company sell are dive watches – they have found their speciality and are sticking with what they are good at, rather than diversifying into pilot or dress watches. They have found success in a specific market and are building their reputation there. Based on this watch, their reputation is outstanding!

The watch up for review now, the Deep Blue Daynight Mil T-100, has been designed and rated to withstand depths of up to 500m/ 1650 feet. Other watches in the range go much deeper, if you have the specific need… The watch has Precision Diver etched onto the rear of the case and it certainly seems to look as if it would be able to be up to the task. It is designed primarily to be sturdy enough to matter in a life or death moment! The value for money that these watches offer make them a must-have to add to any watch collection, not only if diving watches are your love. The watch feels rock solid with a bit of a vintage retro feel to it. Functionality seems to be the driving force behind the key design but it also looks rather amazing as a chunky timepiece on the wrist. Forms truly does follow function in this watch.

The 45mm case size is made from 316L Stainless Steel. The case depth of 15mm means that it is not a diminutive watch by any means but just keep reminding yourself what the watch is actually designed to be used for. Lug to lug length is 53mm and it takes a 22mm strap, which allows you to experiment with a host of other options to hold it securely on your wrist. The unidirectional 120 click bezel moves with a satisfying and secure click anti-clockwise and you just ‘know’ it is going to remain exactly where you set it. The lug guard protected crown is screw-in to secure the internals of the watch if you feel the need to wear it whilst exploring the ocean floor. The etched caseback is also screw-on. The 33mm wide dial, protected by sapphire crystal, is matt black with white minute markers for easy legibility in daylight but it is in total darkness that the watch comes into its own…

Tritium has been used by other watch manufacturers, from Rolex to Ball, but generally is found on quite expensive watches. Deep Blue have been committed to sharing Tritium watches at a more affordable price-point. T-100 Tritium tubes glow green on all of the indices and hands. The double indices at the 12 o’clock position glow orange of spacial awareness in complete darkness. There is also a Tritium pip tubes embedded into the bezel. Deep blue offer two options for Tritium tubes, which are Swiss manufactured. The smaller T-25 are on the entry-level watches and the larger T-100 that can be seen on this watch and give it part of it’s name. The company states that T-25 will hold its luminosity for around 20 years in the tiny vials on the dial and that T-100 will have a shelf life of around 50 years. Well, you may ask, what happens after 20 years? Well, as the vials are on the dial, a new dial can easily be placed into the watch when it is serviced and the Tritium glow is, quite literally, reset.

The movement is a Seiko NH35 automatic mechanical one. With date function as well, the 24 jewelled engine inside offers a 40-hour power reserve. Housed in such a protective case, it will survive most ways you could imagine to treat this watch.


  • A no-nonsense watch that is designed to do a job and do it well.
  • Tritium tubes – just a bit cool and different from most other watches. The variety of colours adds to this.
  • Seiko NH35 movement – very reliable


  • It is a thick watch with a lot of wrist presence. However, you need to remember what this watch was designed to do!

Buy a Deep Blue Daynight Mil T-100

Just to tempt you a little more with a bargain… At the moment, Page And Cooper ( are offering 10% off the entire range of Deep Blue watches with the discount code: CAS10

By Keith Campbell

After spending 16 years circumnavigating the globe and going up-diddly-up as part of the Royal Air Force, Keith became a Professional Aviation Photographer. His natural progression to watch product photography came after companies approached him due to the images he was creating of his own watch collection with an aviation theme. He now works with over 50 watch brands, from the majors to micro brands. His aviation (and Star Wars) work can be found and purchased via his website at along with @captureasecond on both Instagram and Twitter. Worth following out of morbid curiosity!

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