Tissot Seastar watches

Seastar is Tissot's water sports line, and every model is rated to at least 30 bar (300 metres). The Seastar 1000 makes up most of the collection, with quartz and Powermatic 80 automatic movements in sizes from 36 mm to 45.5 mm, including a 40 mm quartz GMT and quartz chronographs in 38 mm and 45.5 mm. The Seastar 2000 Professional, first introduced in 2021, sits at the top. It is certified to the ISO 6425:2018 dive watch standard, rated to 600 metres, and uses a 44 mm steel case with a helium escape valve, a ceramic bezel insert and the Powermatic 80 with a Nivachron balance spring.

Sources: Tissot Seastar collection, The Tissot Seastar 2000 Professional: Five New Editions, Tissot Seastar 1000 40mm Powermatic 80, Manufacturer product page, Manufacturer product page, Manufacturer product page