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Seiko Prospex Sumo SPB103 vs Halios Seaforth

Both are dive watches in the upper tier. In short: the Seiko Prospex Sumo SPB103 wears 45mm vs the Halios Seaforth's 41mm — choose by wrist size. The Seiko Prospex Sumo SPB103 is automatic, 200m water resistance, 45mm, sapphire crystal; the Halios Seaforth is automatic, 200m water resistance, 41mm, sapphire crystal.

Last verified 2026-06-27 · specs from manufacturer data · tier = price band, confirm the live price at the retailer

SpecSeiko Prospex Sumo SPB103Halios Seaforth
MovementAutomaticAutomatic
Water resistance200m200m
Case size45mm41mm
Crystalsapphiresapphire
StyleDiveDive
Price tierUpperUpper

Which should you buy?

The Seiko Prospex Sumo SPB103 wears 45mm vs the Halios Seaforth's 41mm — choose by wrist size.

Where to buy

Seiko Prospex Sumo SPB103See price on AmazonCheck price

Halios SeaforthSee price on AmazonCheck price

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FAQ

What's the difference between the Seiko Prospex Sumo SPB103 and the Halios Seaforth?
Both are dive watches in the upper tier. The Seiko Prospex Sumo SPB103 is automatic, 200m water resistance, 45mm, sapphire crystal; the Halios Seaforth is automatic, 200m water resistance, 41mm, sapphire crystal.

Which is better value, the Seiko Prospex Sumo SPB103 or the Halios Seaforth?
Both sit in the upper tier, so it comes down to movement, water resistance and case size — see the spec table above.

Citing these specs? Go ahead — manufacturer data, last verified 2026-06-27. Copy a ready-made reference:

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