Tuna

The Seiko Tuna is a family built around a protective outer shroud: that unmistakable ring gives the watch its nickname and shields the case from knocks. Beneath it, the range stretches from large professional saturation divers to smaller everyday divers, with automatic and quartz movements across several generations.

The starting point is the 1975 6159-7010, a titanium, 600-meter automatic diver whose construction addressed the demands of saturation diving without a helium-release valve. Quartz joined the family in 1978, establishing a second lineage rather than replacing the mechanical one. Later professional models pushed depth ratings to 1,000 meters; their broad shrouds and compact lug arrangements make diameter alone a poor guide to how they sit on the wrist.

Enthusiast names such as Golden Tuna, Emperor Tuna, and Baby Tuna help navigate the branches, but they are nicknames, not a uniform specification. Smaller automatic models such as SBDY073 carry the shrouded design into a different category from the deep-diving professional watches. Movement type, depth rating, and case construction are the useful dividing lines between generations that can look remarkably similar at first glance.