The Seiko Prospex Sumo SPB103J1 is part of Seiko's extensive and legendary diving watch collection, and has received the heavyweight nickname of 'Sumo'. Another nickname that was, perhaps more kindly, bestowed upon it was 'MM200', which is short for MarineMaster 200 (200 for the water resistance, as the Marinemaster itself is 300m water resistant). The Marinemaster is Seiko's their high-end, no limits, diving watch that has garnered an incredible amount of praise over the years for being one of the best diving watches out there. That does set the bar pretty high for a watch at around 1/4th the price.

Is this watch as good as a 'real' Marinemaster? No, but it does punch above it's weightclass, regardless of being a 'Sumo. To start, it's a healthy 45mm in diameter, with a lug to lug distance of 52.6mm. That does mean it has a fairly substantial wrist presence, which is generally agreeable for a serious diving watch. 200m water resistance, a sapphire crystal and a high level of finishing are all part of the boxes that you can check on your 'diving watch wishlist'. What shouldn't be forgotten especially is the engine that powers this beast; the Seiko in-house Cal. 6R35 mechanical, automatic, movement, which features an impressive 70 hour power reserve. Definitely a drivetrain you can rely on.

The Sumo features great lume and a very legible, utilitarian design that is ideal when diving and for every day practicality. There is little chance you won't know what time it is!