If your collection is going to be one watch, it should be able to do everything. The Marathon 36mm OSAR-D, reference WW194026SS-2005, is a strong candidate: a black-dial Swiss automatic diver on a stainless steel bracelet that looks right at work, on weekends and in the water.

A one-watch collection lives or dies on versatility, and the OSAR-D covers the bases. The black dial with clean geometric indices is neutral enough for business casual, the brushed steel bracelet handles daily wear without fuss, and 300 meters of water resistance means you never need to take it off for a swim. The cyclops-magnified date at 3 o'clock is practical for everyday life, and the self-winding Sellita SW200-1 movement means no batteries to replace. Wear it daily and it simply keeps going.

The heritage gives it substance. The OSAR-D descends from the SAR-D that Canadian Search and Rescue Technicians wore in the early 2000s, and Marathon has been making military watches since its first RCAF order in 1941. Today's version, relaunched in 2024, adds MaraGlo lume, larger indices and the improved cyclops date. At 36mm across and 13mm thick, it remains slim enough to slide under a cuff.

Everyday Specs: Marathon OSAR-D WW194026SS-2005

• Case size: 36mm, 13mm thick, 43.5mm lug to lug
• Material: brushed 316L stainless steel
• Movement: Sellita SW200-1 Swiss automatic, 26 jewels, about 41 hours, Incabloc
• Water resistance: 30 ATM / 300m
• Crystal: sapphire with date cyclops
• Lume: MaraGlo
• Dial: black Type I, date at 3
• Bracelet: stainless steel, 18mm lugs

One watch, every occasion, no compromises.