Choose the 40 mm Seastar 1000 automatic for everyday wear and recreational water use. Choose the 44 mm Seastar 2000 Professional when ISO 6425:2018 certification, a 60 bar (600 m) rating and saturation-diving features matter to you, and you prefer its larger case.
This comparison uses Tissot's current reference-level specifications. Wrist fit, bezel feel and underwater performance were not independently tested.
This comparison centres on two exact references: the 40 mm T120.807.11.051.00 and the 44 mm T120.907.17.041.00. Tissot also makes 43 mm and 46 mm alternatives, and a thinner 40 mm quartz Seastar 1000. Their dimensions and materials differ, so check the reference rather than relying on the family name.
Before taking either watch into water, follow its instructions and make sure its water resistance is in good condition. A printed rating is not a guarantee of a safe diving depth.
40 mm Seastar 1000 versus 44 mm Seastar 2000 Professional
| Specification | Seastar 1000 automatic | Seastar 2000 Professional |
|---|---|---|
| Reference | T120.807.11.051.00 | T120.907.17.041.00 |
| Case diameter | 40 mm | 44 mm |
| Case thickness | 12.48 mm | 15.29 mm |
| Movement | Powermatic 80 automatic | Powermatic 80 automatic |
| Power reserve | Up to 80 hours | Up to 80 hours |
| Water-resistance rating | 30 bar (300 m) | 60 bar (600 m) |
| Bezel ring | Mineral glass | Ceramic |
| Front crystal | Sapphire | Sapphire |
Sources: Tissot's 40 mm Seastar 1000 specification and 44 mm Seastar 2000 Professional specification. Reserve depends on available stored energy; a partly wound watch may stop sooner.
The 40 mm automatic is 4 mm narrower and 2.81 mm thinner than the 44 mm Professional. That helps narrow the choice if you want a smaller watch or need clearance under a cuff. It does not establish which will feel comfortable on your wrist: try the exact case and bracelet or strap before deciding. These dimensions alone also do not tell you which strap configuration is lighter.
What the 2000 Professional adds
Tissot lists the 44 mm Professional as ISO 6425:2018 certified, with a 60 bar (600 m) rating and a helium valve. The valve allows helium to escape during decompression after saturation diving. It is a specialised feature; ordinary swimming and recreational water use do not require it. Tissot explains the feature on the 44 mm Professional page.
The Professional also has a ceramic bezel ring. The 40 mm automatic 1000 uses mineral glass in its bezel ring, even though both watches have sapphire front crystals. The bezel ring and the glass over the dial are separate components. If ceramic is a buying priority, do not assume that every automatic Seastar 1000 has it: the 43 mm reference below does, while this 40 mm reference does not. Material labels alone do not establish how a bezel will withstand every scratch or impact.
Both main references offer the Powermatic 80 automatic movement with up to 80 hours of reserve. A well-wound watch can therefore spend time off the wrist, but a partly wound watch may stop sooner and need winding and resetting. The reserve figure does not guarantee Monday-morning running after any Friday removal, or tell you how accurately the watch will keep time. Buying the Professional does not add reserve over the 40 mm automatic compared here.
The 43 mm, 46 mm and quartz alternatives
Choose the 43 mm Seastar 1000 automatic T120.407.11.051.00 if you prefer a larger 1000 and want a ceramic bezel. Tissot lists it at 12.70 mm thick, distinct from the 40 mm automatic's 12.48 mm. See its official specification. Try it on rather than treating the extra diameter as a promise of better fit or legibility.
The 46 mm Seastar 2000 Professional T120.607.11.041.00 is the larger Professional option. It is 16.25 mm thick, with a ceramic bezel, 60 bar (600 m) rating and up to 80 hours of reserve. Those figures come from Tissot's 46 mm specification. Its greater thickness deserves a separate try-on; the 44 mm model provides another route to the Professional's diving features.
For a thinner 40 mm watch, consider the Seastar 1000 quartz T120.410.11.041.00. It is 9.97 mm thick, rated at 30 bar (300 m), and has an end-of-battery-life indicator, according to its Tissot specification. Quartz requires no winding, though its battery will eventually need replacement. It is a practical option for occasional wear; choose automatic if owning and winding a mechanical watch is part of the appeal. If you are considering a different everyday Tissot style, our Chemin des Tourelles guide covers that alternative.
Water use and care
Tissot bases water-resistance ratings on laboratory pressure tests and notes that changing conditions, ageing gaskets and damage to the crown can affect protection. Neither 300 m nor 600 m should be read as permission to dive to that depth. For diving, follow the exact watch instructions and your activity's equipment requirements; the higher number does not replace checking the watch's condition.
Do not operate the crown or pushers underwater. After setting, secure the crown as instructed. After sea use, Tissot recommends rinsing the watch with warm fresh water and drying it completely. The brand recommends an annual water-resistance check by an authorised Tissot service centre. See its care and water-resistance guidance, alongside the manual for your reference.
Choosing your Seastar
Start with the 40 mm automatic 1000 if you want an automatic sports watch and prioritise a smaller case. Consider the 43 mm automatic if you want a larger 1000 with a ceramic bezel, or the 40 mm quartz if thinness and occasional-wear convenience come first.
Choose the 44 mm Professional for its ISO certification, ceramic bezel and saturation-diving valve, accepting the larger case as part of the purchase. The 46 mm Professional is an additional size choice, rather than a necessary step up from the 44 mm model.
Browse the Tissot Seastar collection or Seastar 1000 collection to compare references. For alternatives beyond this family, see our guides to Swiss automatic divers and dive watches.