Casio G-Shock GA-B2100 CasiOak vs Tissot Seastar 1000 Automatic
Two divers compared — $100–$150 vs $500–$1,000
Quick Verdict
The Casio G-Shock GA-B2100 CasiOak ($100–$150) offers Casio Quartz (Solar-Powered) precision in the tier below the Tissot Seastar 1000 Automatic ($500–$1,000). The G-Shock GA-B2100 CasiOak measures 45.4mm (48.5mm lug-to-lug, 11.9mm thick) and is rated 200m (20 ATM). The Seastar 1000 Automatic counters with Swiss Made craftsmanship and 300m (30 ATM) water resistance. Both are exceptional divers for their respective tiers.
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Specifications Compared
| Feature | Casio G-Shock GA-B2100 CasiOak | Tissot Seastar 1000 Automatic |
|---|---|---|
| Price | $100–$150 | $500–$1,000 |
| Case Size | 45.4mm (48.5mm lug-to-lug, 11.9mm thick) | 40mm |
| Movement | Quartz Module 5689 (Tough Solar + Bluetooth) | Automatic Powermatic 80 (Caliber 80.111) |
| Caliber Type | Casio Quartz (Solar-Powered) | ETA/Tissot Automatic |
| Power Reserve | About 7 months on a full charge without light; about 18 months in power-saving (Casio) | 80 Hours |
| Water Resistance | 200m (20 ATM) | 300m (30 ATM) |
| Crystal | Mineral Glass | Sapphire Crystal |
| Case Material | Carbon Core Guard Resin | Stainless Steel |
| Origin | Made in Japan | Swiss Made |
Category-by-Category Analysis
Design & Aesthetics
Casio's design language vs Tissot's approach
The Casio G-Shock GA-B2100 CasiOak features a Carbon Core Guard Resin case at 45.4mm (48.5mm lug-to-lug, 11.9mm thick) with Mineral Glass protection. The Tissot Seastar 1000 Automatic offers Stainless Steel construction at 40mm with Sapphire Crystal. Both represent their brand's distinct design philosophy and heritage.
Movement & Performance
Quartz Module 5689 (Tough Solar + Bluetooth) vs Automatic Powermatic 80 (Caliber 80.111)
The G-Shock GA-B2100 CasiOak runs the Quartz Module 5689 (Tough Solar + Bluetooth) (Casio Quartz (Solar-Powered), About 7 months on a full charge without light; about 18 months in power-saving (Casio) power reserve) at standard frequency. The Seastar 1000 Automatic uses the Automatic Powermatic 80 (Caliber 80.111) (ETA/Tissot Automatic, 80 Hours reserve) at 21,600 vph (3 Hz). The Seastar 1000 Automatic offers a longer power reserve.
Wearability & Fit
45.4mm (48.5mm lug-to-lug, 11.9mm thick) vs 40mm — different wrist presence
At 45.4mm (48.5mm lug-to-lug, 11.9mm thick), the G-Shock GA-B2100 CasiOak has a bolder wrist presence compared to the Seastar 1000 Automatic at 40mm. Water resistance differs: 200m (20 ATM) vs 300m (30 ATM).
Value & Cost of Ownership
Casio sits in the lower tier
The Casio G-Shock GA-B2100 CasiOak sits at $100–$150 and the Tissot Seastar 1000 Automatic at $500–$1,000. On the specs that outlast any price: the G-Shock GA-B2100 CasiOak uses Mineral Glass with About 7 months on a full charge without light; about 18 months in power-saving (Casio), against Sapphire Crystal and 80 Hours on the Seastar 1000 Automatic. Service intervals are typically 5-7 years for both.
Water Resistance
200m (20 ATM) vs 300m (30 ATM)
The G-Shock GA-B2100 CasiOak is rated to 200m (20 ATM) while the Seastar 1000 Automatic handles 300m (30 ATM). The Seastar 1000 Automatic offers superior water resistance.
Our Verdict
Casio
G-Shock GA-B2100 CasiOak
Choose the Casio G-Shock GA-B2100 CasiOak if you prioritize Casio Quartz (Solar-Powered) engineering, Made in Japan craftsmanship, and 200m (20 ATM) water resistance. At $100–$150, it delivers Quartz Module 5689 (Tough Solar + Bluetooth) with About 7 months on a full charge without light; about 18 months in power-saving (Casio) power reserve.
Check Price on AmazonTissot
Seastar 1000 Automatic
Choose the Tissot Seastar 1000 Automatic if you value ETA/Tissot Automatic technology, Swiss Made heritage, and 40mm proportions. At $500–$1,000, the Automatic Powermatic 80 (Caliber 80.111) with 80 Hours power reserve makes it a compelling choice.
Check Price on AmazonThe Bottom Line
The Casio G-Shock GA-B2100 CasiOak and Tissot Seastar 1000 Automatic represent two distinct approaches to the diver category — the Casio bringing Made in Japan tradition while Tissot delivers Swiss Made engineering.
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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.