Titus Welliver as Harry Bosch wears a Rolex Submariner watch throughout the series Bosch and Bosch: Legacy.
It's possible that he wore different model variations, but in the later seasons it seems to be the Rolex Submariner Date 116610LN with black ceramic bezel.
The Rolex Submariner is an all time iconic watch, famously worn by James Bond and many other celebrities.
A Rolex Submariner Date 116610LN will set you back anywhere between $11,000 and $20,000 on Chrono24 or on JomaShop.
Some affordable alternatives / homage watches are the Invicta watches (on Amazon for $86). A more unique but great looking affordable alternative is the Casio Duro MDV106 (on Amazon for $49).