Captain Sonar is, ideally, an 8-player realtime board game where two teams of four take command of a submarine each and try to blow the other team out of the water. The four crew of each submarine are:
The Captain, who calls out directional orders for her boat and watches in dispair as her and her crew spiral into an inescapable, crushing darkness.
The Radio Operator, who listens to the increasingly uncertain commands of the enemy captain and attempts to discover the location of the opposing vessel, mostly through a haze of frustrated head-scratching and sudden clarity, akin to solving a 1,000 piece jigsaw puzzle.
The First Mate, who is tasked with making ready the various systems on the submersible, and then politely informing the captain she can't use them because everything is broken and/or on fire.
The Engineer, who breaks things constantly, much like some sort of traitorous gremlin.
By working as a team, or at least a horribly faded facsimile of one, you hope to inflict four points of damage to the enemy first, crushing them within their steel sarcophagus under tonnes of seawater.
Played in realtime with a full player count, Captain Sonar, by Matagot, runs at about 30 minutes, the first 25 of which see both teams travelling the frigid depths, oblivious to their opponents true location, before ending in a burst of adrenaline and excitement as everything suddenly clicks into place on both sides of the table. It is crazy, chaotic, frustrating and utterly, absolutely, insanely genius.
The first time I played Captain Sonar was with six players, one of whom was probably too young for the game. This resulted in a 3 versus 2.5 player game. It ran longer than hoped, mostly because I was teaching and learning how best to teach it along the way. The second and third had eight players, but also ran well over 30 minutes each, for a few reasons, none of which were the games fault.
Games four through nine however were much more how I imagined the game would play from reviews I had seen. Games four, five and six were all fast, frantic and unbelievably hilarious, with everyone howling with laugher whether they were on the winning boat or not. This, despite those games being played in a noisy convention hall among 200-odd other gamers. Games seven, eight and nine were equally fast, in a room with just the eight players present, but ended with some tension, not due to the game, but to the mix of personalities present.
Captain Sonar is a fun party game and should absolutely be treated like that. Don't over-think actions, or get annoyed when someone on the other team makes a mistake. Laugh and congratulate your opponents, win or lose, and then challenge them to a rematch. Don't worry if you're feeling lost in your first game at the start. You're supposed to feel like that. Trust me, the other team feels the same way.
If there is a fatal flaw to Captain Sonar it is the player count. Dispite the box proclaiming it to be for 2-8 players, you really do need eight players to have the most fun, which is fine as long as you treat it like a party game, only played when you have lots of people around. And play it in realtime. There is a turn-based varient, but use that to run through a few sample rounds before pushing into realtime as soon as possible.
The artwork is beautiful where there is artwork, the roles are hilarious, the player interaction is chaotic and the game has become a huge favourite in my collection, after a short rocky start almost beached it. I've only owned it since Christmas, and with nine games played already, I don't have any other game that I've played that much in that short a time since, probably BattleStar Galactica The Board Game was released. And if that isn't a huge endosement, I don't know what is!!
Amazing YouTube board game review (mostly) channel No Time For Games has a wonderful short on Captain Sonar. Watch it below, then go and watch everything he's made (there's not that many and they're all short) and then subscribe, because this guy deserves more fans.
 Maybe even 3vrs2, because one of the players on that team was splitting his time between his own station and watching and correcting her station, diminishing his role effectiveness in the process too.
 Missed rules and language barriers mostly, though also hard-core gamers over thinking things a bit.
 I weep at the thought of playing it as a 2-player game.
 I highly recommend his Inis video.