Goalball is considered part of the spectrum of athletic endeavors called blind sports, and it is akin to tennis, combined with soccer goaltending. It's visually exciting, but to truly appreciate it one has to understand some of the nuances of the game.
It is played indoors, on a playing surface akin to a basketball court, with markings laid out with tape overlaying string or thin rope, providing a tactile as well as visual boundary and positional markings. There is a goal at each end, 18m apart on a field 9m wide. Each goal spans the entire 9m of the playing field, and the field between the two is divided into six equal sections. The section closest to a team goal is the team's section, the next one is the landing section, and the middle is a neutral zone. The next is again the neutral zone, then the opposing team's landing section, then the opposing team's section.
Hash marks on the field allow players to orient themselves spatially, and often a player will back into the (padded) goal to orient his or herself in terms of where the field begins. The object of the game is to score as many points in two 12 minute periods as possible, and the team with the most points wins. A player in possession of the ball has ten seconds in which to launch the ball towards the opponents' goal (or incurs a penalty). The ball must land in the team's own landing zone, pass through each othe other zones enroute to the goal, and hopefully make it past all three players and into the goal.
There are three players per team, and they usually align themselves to cover a third of the goal, either in terms of attack or defense. The center player often coordinates.
The players from the opposing team do not allow themselves to be scored upon: they typically throw themselves in the path of the oncoming ball, lying flat on one side with arms and legs outstretched. Players are padded, especially on the sides (as they throw themselves to the ground repeatedly) but also in other vital areas, including the eyes, in case of the ball coming into contact with them.
The ball is 24cm in circumference and weighs in at one and a quarter kilograms. It is made of rubber and contains multiple bells, to allow for all players to locate the ball as it is either bowled at the opponent's goal, incoming towards one's own goal, or dropped or passed to a teammate. It is an infraction for the ball to pass outside the field of play on the sidelines when being passed from player to player, and it is also theoretically possible to score an own goal, so it is important to make sure the other player can echo-locate the ball during a pass.
Regardless of how blind a player actually is, typically the eyes are taped (especially in the instance of a sighted player) and the eyes covered with opaque goggles. Blindness is a spectrum - some can be legally blind but still respond enough to movement and color to have some advantage. Also, the game is not restricted to the blind, in theory and in practice there are fully sighted players. But the equipment in the game assures that regardless of the level of vision, be it full, impaired, legally blind or fully blind, no player can see in any way shape or form at all. Should a player's blindfold or goggles be dislodged, he is to call this to the attention of a referee, who will come over and ensure the player is 100% blind before play resumes.
Referees are sighted, and there are two of them. All officials are sighted: these include two goal judges at each end, a timer, a backup timer, and a scorekeeper. It is imperative that a team attempts to score within ten seconds of acquiring it, making for a fast-paced game.
If the score is tied at the end of two twelve minute periods (merciful, considering the breakneck pace and speed) there are two three minute overtime periods, in which the first team to score wins. Should one team be outscoring the other by ten points or more, the "mercy rule" is invoked and the game ends.
A blind fan asked me once, as I was volunteering at a game, if it was as visually exciting as it was to hear. It is indeed. Players are no less aggressive for being blind: they'll dive in the path of the ball, back up and bounce off the (padded) goal in order to orient quickly, and bowl the ball with some velocity. In order to obtain more speed and also confuse the other team, some players will spin around and then throw the ball, making it maddeningly difficult to echo-locate where the ball is coming from. You don't have that much time either - some players can bowl the ball at 60 kilometers per hour or more. And you have to make sure you dive in the path of the ball, with some overlap behind and before, without players colliding.
Once the ball hits, in can bounce - either over the player for a goal, offside to the side, or within reach and the players scramble for it. Somehow these teams managed to know just who is going to go grab the ball, and they seem to not even need to whip a hand out to feel the field for the sideline or an orienting hash mark - they almost preternaturally know. So the ball blazes down the court, hits a player, bounces. He gathers it, backs up, spins, hurls it back with equal ferocity and scrambles back to his original defensive position.
Whereas I could see the player's hair furiously whipping as he acrobatically threw the ball downfield, and marvelled at the sweat pouring off these guys as they ran, jostled, and threw themselves violently at the floor, the fan I was with could more experience the game as the players do - tracking the ball and players purely by sound.
Apart from infractions relating to improper throws (the ball being too high and not landing in the team's own landing zone and the neutral zone), or delay of game, or taking too long to throw the ball back, there are a few rules that pertain to the nature of the game and cheating. You cannot throw the ball until the referee calls to throw the ball, you cannot make excessive noise to prevent the other team from tracking the ball. Touching your eye-goggles is also explicitly not allowed, you may only have the referee adjust goggles once the game has begun.
I admit I watch a sport for the blind, as awkward and as weird as that sounds. It's not only a national sport, but an international and even a Paralympic sport. If you do get the chance to check out a game, do by all means go and experience this. You will however have to keep your cheering to yourself.