Supermarine S301

The Supermarine S301 is Bremont's serious professional diver: 300 metres of water resistance, a unidirectional ceramic bezel, and a compact 40mm steel case that keeps the whole package wearable. It sits at the credible end of Bremont's lineup, where the brand's naval associations feel earned rather than decorative. If you want a British-designed dive watch that fits under a wetsuit and doesn't require a second mortgage, the S301 is the honest answer.

What it is

Bremont was founded in 2002 by brothers Nick and Giles English, named after a French farmer who sheltered their father's damaged plane in a field. The brand built its identity around aviation and military heritage, supplying watches to British armed forces units and earning official supplier status with several defence organisations. The Supermarine line came later, extending that service-watch ethos into diving.

The S301 in its current 40mm form launched in 2021, replacing bulkier earlier Supermarine references that had pushed 43mm. The black-dialled S301-BK reflects genuine demand for a compact, legible professional diver that doesn't announce itself the moment you walk into a room.

Buying notes

Bremont prices the S301 at a significant premium over competitors running the same Sellita SW300-1 base movement, and buyers should understand what they are paying for: design, heritage association, and British assembly, not a proprietary caliber. The BE-92AE designation is Bremont's name for the modified Sellita; it is a solid movement, but the modification level is incremental. Secondary market values have historically softened more than the brand's positioning suggests they should, so buying grey at a meaningful discount to retail is both common and sensible.

The black PVD-adjacent finishing on some components of the S301-BK deserves inspection on pre-owned examples, as heavier wear on case edges can be difficult to restore invisibly. Finally, confirm the ceramic bezel insert is intact and scratch-free before buying used, since replacement through Bremont service is not inexpensive.

Market read

New S301-BK references retail in the $3,000–$3,500 range depending on region and dealer. Grey market pricing typically lands 15–25% below that, which is where this watch makes the most sense as a purchase. Demand is steady but not frantic, so patient buyers can find clean examples without urgency.

Resale liquidity is adequate but not strong: this is a watch to buy because you want to wear it, not because you expect appreciation.

Service expectations

The S301 runs the BE-92AE caliber, Bremont's designation for a modified Sellita SW300-1. Service intervals are typically 5–7 years, and the movement is well-supported by both Bremont's UK service centre and independent watchmakers familiar with Sellita architecture. Pressure-testing after any case opening is essential given the 300m water resistance rating.