Designed for saturation diving up to a depth of 600m, Grand Seiko’s professional diver’s watch SBGH255 features a tough, high-intensity-titanium case construction that is impervious to penetration from gas, air, and water. The watch also features a high degree of anti-magnetism due to its pure iron dial, and there’s a crown at four o’clock for safety and comfort. The grooves on the rotating bezel ensure a firm grip even with thick diving gloves, and the case, stem, and crown are designed for simple servicing. Even the bezel has a four-part design that makes for easy disassembly and re-assembly. The dial’s mirror-polished dot pattern is reminiscent of air bubbles rising to the surface during a dive, and luminous markers ensure legibility, a critical feature of any serious diver's watch. This professional diver's model utilizes Caliber 9S85, a high frequency "Hi-Beat" movement with a beat rate of 36,000 bph, and a precision rating of +5 to -3 seconds a day.