Water polo is supposed to be fair. There are even referees. But tales of what goes on beneath the pool surface are impossible to ignore. Most who have played the game will testify that the gents tend not to remain strangers to each other's tender regions. For the women, "nipple-screwing" is a persistent bane.
All the more surprising that for lengthy periods it proceeds with perfect serenity. One player glides forward, head erect, ball guarded between front-crawling arms, before it is switched from one side of the pool to the other in one-handed throws and catches – not an easy thing to do with a large ball while treading water –searching for an opening in the defensive ranks. But the threat of violence lurks, and nearly anything can summon it.
A misplaced pass, a dropped catch, and the ball turns loose. Anyone who has ever casually tossed anything edible into a Mediterranean marina will recognise the scene.
The water foams, concealing the worst of the crimes, in a melee of twisting, writhing, grabbing, slapping and, it is commonly accepted, punching and kicking, before inevitably a whistle blows, and the same fractious drama plays out again.
Britain was once the home of waterpolo. We have won four Olympic golds in the game, which leaves us fourth in the overall medal table, but the last one came in 1920. We have not entered a team since the 1956 Games in Melbourne. It was in that tournament that Hungary fought (a word used figuratively so often in sport, but not in this case) the Soviet Union for the gold medal just weeks after the tanks had rolled into Budapest, crushing a popular uprising there. Hundreds of Hungarians had been killed, thousands more arrested.
With 5,000 Hungarian-Australians supporting their compatriots, the Soviet player Valentin Prokopov almost sparked a riot when he punched the Hungarian team's star player, Ervin Zador. "A whistle came, I looked at the referee, I said 'What's the whistle for?' And the moment I did that, I knew I'd made a horrible mistake," recalled Zador, years later. "I turned back and with a straight arm, he [Prokopov] just smacked me in the face. He tried to punch me out."
Prokopov drew no small amount of blood. Zador was carried from the pool as spectators and Hungarian officials stormed towards the Russian team, who had to be rescued by the Australian police.
This time round, as hosts, Britain have been rather obliged to enter the competition. Rather them than us. On Sunday night the men were given something of an education by the Romanians, losing 13-4.
Often at the Olympics, the waterpolo matches are contested in a roped-off section of the main aquatics arena. Despite our obvious failings at the games, we have constructed a purpose-built, albeit temporary home for the sport. From the outside, it is a thick wedge of cheese, wrapped in cling film. Inside, 5,000 spectators sit in one large bank of seats sloping down to the poolside, affording a superior view of the fighting.
Last night the TeamGB women took on Russia. Elsewhere in the group lie the Italians, and the Australians, with whom there is bad blood, after TeamGB's Alex Rutlidge suffered a broken rib in a 5-0 defeat to them two months ago.
"We've got it on film," said team-mate Frankie Snell. "You can see the girl pull Alex in towards her and then boot off her ribs. You saw Alex almost sink under the water." TeamGB have since been quick to point out they have been practising martial arts.
Intriguingly, Italy's Elisa Casanova, one of the world's great players, thinks the girls might have a chance. "This is not water polo, this is wrestling," she said after her team's narrow 10-8 defeat to Australia yesterday. "It's impossible. If GB play like Australia, with the fighting and the wrestling, the result of every match is open."
The Australian coach Greg McFadden sees it differently. "There's certain rules you've got to learn in water polo," he said, "and if the referees don't apply those rules, the player have to take it into their own hands."
1956: Hungary vs Soviet Union
Hungarian gold medallist Ervin Zador says his team's gameplan against the Soviet Union revolved around "verbally agitating" the Russian players. It worked. Shortly before the end Valentin Prokopov punched him square in the face. Zador was carried from the pool bleeding profusely while the Russians had to be saved from the Hungarians – and the crowd – by a police escort.
2009: USA vs Canada
With the score tied at 4-4 in the world championship final, Elsie Wildes scored to give USA the lead, then landed a hard right to the jaw of Canadian captain Krystina Alogbo. Ms Wildes was "excluded" but the punch was deemed merely "violence" and not "brutality", so she faced 20 seconds, rather than four minutes, in the sin bin.