The Colorado is an American submarine that's just completed a rescue of several Navy SEALs when they receive an order to fire four nuclear missiles on Pakistan. There are some procedural irregularities in the orders, and when Captain Marcus Chaplin (Andre Braugher) and his executive officer Sam Kendal (Scott Speedman) request confirmation, they are fired on by an American warship.
A lot happens in this first hour, and there's a fair amount of military jargon, but the gist of events is always clear, and the activity doesn't come at the expense of character development. The first half hour, as the crew tries to make sense of its puzzling orders, is particularly well done, and does a fine job of building tension.
There's a large ensemble cast (the sub's crew is 150, after all), and it's sometimes a little hard to tell people apart; the standard problem of military dramas pops up -- lots of fit young men with short haircuts (not that I have any objection to fit young men, mind you, regardless of hairstyle) -- but is somewhat mitigated by the fact that the crew is very diverse.
From that large group, it seems likely that the central figures will include Lt. Grace Shepard (Daisy Betts), an admiral's daughter fighting to be respected in a male-dominated culture; Joseph Prosser (Robert Patrick), a senior officer who seems likely to be in frequent conflict with Chaplin and Kendal; defense contractor Kylie Sinclair (Autumn Reeser); James King (Daniel Lissing), one of the rescued SEALs, who seems to know more than he'll admit about what's really going on; and Julian Serrat (Sahr Ngaujah), the local strongman on a small island which houses a NATO observation post.
The casting is very good; Braugher and Speedman have an instantly believable working relationship, and both convey the necessary authority. Betts manages the tricky problem of confronting her sexist colleagues in a way that comes across as assertive but not bitchy (and she's helped by the fact that the character's well written). Nguajah's role is potentially problematic, and could come off as a cheap tropical gangster cliche if not carefully handled, but my first impression is that he's up to the challenge.
Whether the show can sustain this level is an open question, of course; there's always the risk that it winds up chasing its own mythology in circles. But even if it does, the first episode is a darned good hour of TV, and well worth your time.