Seiko watch prospex marinemaster professional 1000m tuna prospex marinemaster celebrates 50 years of seikos divers watch excellence it was in 1965 that seiko made its first ever divers watch half a century on the list of seikos achievements in this most challenging of arenas for watchmakers is long and distinguished from the first use of a titanium case for a divers watch to the invention of the accordion style strap and the two layer case to the design of dial markers and hands of unparall