Head-to-Head Comparison

Updated September 5, 2026

Citizen Promaster Sea Eco-Drive Diver vs Seiko 5 Sports GMT SSK001

Citizen's diver meets Seiko's GMT watch

Quick Verdict

The Citizen Promaster Sea Eco-Drive Diver ($250–$500) and Seiko 5 Sports GMT SSK001 ($250–$500) are closely matched timepieces at similar price points. The Promaster Sea Eco-Drive Diver emphasizes Citizen Eco-Drive (Solar Quartz) engineering while the 5 Sports GMT SSK001 focuses on Made in Japan craftsmanship.

CitizenPromaster Sea Eco-Drive Diver$250–$500 Check price Seiko5 Sports GMT SSK001$250–$500 Check price

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Citizen

Promaster Sea Eco-Drive Diver

$250–$500

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Seiko

5 Sports GMT SSK001

$250–$500

Check Price Full Review

Specifications Compared

Feature	Citizen Promaster Sea Eco-Drive Diver	Seiko 5 Sports GMT SSK001
Price	$250–$500	$250–$500
Case Size	44mm	42.5mm
Movement	Eco-Drive Caliber E168	Automatic Caliber 4R34 (True GMT)
Caliber Type	Citizen Eco-Drive (Solar Quartz)	Seiko In-House Automatic GMT
Power Reserve	—	41 Hours
Water Resistance	200m (20 ATM) ISO 6425	100m (10 ATM)
Crystal	Mineral Crystal	Hardlex Crystal
Case Material	Stainless Steel	Stainless Steel
Origin	Made in Japan	Made in Japan

Category-by-Category Analysis

🎨

Design & Aesthetics

Edge: Draw

Citizen's design language vs Seiko's approach

The Citizen Promaster Sea Eco-Drive Diver features a Stainless Steel case at 44mm with Mineral Crystal protection. The Seiko 5 Sports GMT SSK001 offers Stainless Steel construction at 42.5mm with Hardlex Crystal. Both represent their brand's distinct design philosophy and heritage.

⚙️

Movement & Performance

Edge: Seiko

Eco-Drive Caliber E168 vs Automatic Caliber 4R34 (True GMT)

The Promaster Sea Eco-Drive Diver runs the Eco-Drive Caliber E168 (Citizen Eco-Drive (Solar Quartz), standard power reserve) at standard frequency. The 5 Sports GMT SSK001 uses the Automatic Caliber 4R34 (True GMT) (Seiko In-House Automatic GMT, 41 Hours reserve) at 21,600 vph (3 Hz). The 5 Sports GMT SSK001 offers a longer power reserve.

📏

Wearability & Fit

Edge: Seiko

44mm vs 42.5mm — different wrist presence

At 44mm, the Promaster Sea Eco-Drive Diver has a bolder wrist presence compared to the 5 Sports GMT SSK001 at 42.5mm. Water resistance differs: 200m (20 ATM) ISO 6425 vs 100m (10 ATM).

💰

Value & Cost of Ownership

Edge: Draw

Same tier — different value propositions

The Citizen Promaster Sea Eco-Drive Diver sits at $250–$500 and the Seiko 5 Sports GMT SSK001 at $250–$500. On the specs that outlast any price: the Promaster Sea Eco-Drive Diver uses Mineral Crystal with a standard reserve, against Hardlex Crystal and 41 Hours on the 5 Sports GMT SSK001. Service intervals are typically 5-7 years for both.

💧

Water Resistance

Edge: Citizen

200m (20 ATM) ISO 6425 vs 100m (10 ATM)

The Promaster Sea Eco-Drive Diver is rated to 200m (20 ATM) ISO 6425 while the 5 Sports GMT SSK001 handles 100m (10 ATM). The Promaster Sea Eco-Drive Diver is better suited for water activities.

Our Verdict

Citizen

Promaster Sea Eco-Drive Diver

Choose the Citizen Promaster Sea Eco-Drive Diver if you prioritize Citizen Eco-Drive (Solar Quartz) engineering, Made in Japan craftsmanship, and 200m (20 ATM) ISO 6425 water resistance. At $250–$500, it delivers Eco-Drive Caliber E168 with solid power reserve.

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Seiko

5 Sports GMT SSK001

Choose the Seiko 5 Sports GMT SSK001 if you value Seiko In-House Automatic GMT technology, Made in Japan heritage, and 42.5mm proportions. At $250–$500, the Automatic Caliber 4R34 (True GMT) with 41 Hours power reserve makes it a compelling choice.

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The Bottom Line

The Citizen Promaster Sea Eco-Drive Diver and Seiko 5 Sports GMT SSK001 represent two distinct approaches to fine watchmaking — the Citizen bringing Made in Japan tradition while Seiko delivers Made in Japan engineering.

Frequently Asked Questions

The Seiko 5 Sports GMT SSK001 is the better buy if you want a mechanical movement; the Citizen Promaster Sea Eco-Drive Diver is the better buy if you want solar power and quartz accuracy with no servicing. For water, the Citizen Promaster Sea Eco-Drive Diver is rated 200 m against 100 m, which is the difference between swimming and diving on one side and splashes on the other. Neither is better at everything; the spec table above shows movement, case size, water resistance and crystal side by side so you can weigh what matters to you. We do not test units, so this is the makers' data, not a bench result.

Both are priced similarly, making this a question of preference rather than value. The Promaster Sea Eco-Drive Diver emphasizes Citizen Eco-Drive (Solar Quartz) technology while the 5 Sports GMT SSK001 prioritizes Seiko In-House Automatic GMT precision.

Both are suitable for daily wear. The Promaster Sea Eco-Drive Diver at 44mm with 200m (20 ATM) ISO 6425 water resistance handles everyday situations. The 5 Sports GMT SSK001 at 42.5mm with 100m (10 ATM) is similarly capable. The Promaster Sea Eco-Drive Diver uses Mineral Crystal while the 5 Sports GMT SSK001 uses Hardlex Crystal.

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How This Page Was Made

Our comparisons are generated from a hand-maintained specification database and reviewed under our editorial standards. We use AI tools to assemble pages from that data. We don’t invent specs: every number traces back to the database, and when we correct an entry, the fix is applied site-wide. As an Amazon Associate, The Horologist earns from qualifying purchases.