On the surface, this is not a spectator sport. From a vantage point beside a public swimming pool in Slovenia, I attempt to make sense of what I am witnessing.

Ostensibly I’m watching a game of hockey. In practice, it’s a confusion of bobbing bottoms and flapping flippers. The energy expended by the two teams is converted into waves that slop against the sides of the pool. There is much splashing, much commotion, but the game itself is beyond sight.

Watching underwater hockey from a poolside is like watching a play from backstage. I only get to see the protagonists when they temporarily leave the action. They recuperate on the surface, face down, breathing through snorkels. Then, with a bob of their bottom and a flap of their flippers, they return to the fray.

The real narrative is being played out on the swimming pool floor. Down there, two teams of six players are vying to push a plastic-covered lead puck toward the goals at either end. Their task is made all the more difficult by the limitations of human physiology. We are not naturally aquatic. As the game progresses, more of the players spend more time at the surface, rasping for breath.

Substitute players sit on a bench like understudies. Dressed in Lycra swimwear, the rest of their costume is piled at their feet: flippers, masks with built-in mouth guards, ear guards, padded gloves and foot-long wooden sticks for pushing the puck. They await the call with a visible mix of impatience and anxiousness.

Underwater hockey was invented almost 50 years ago. Originally played by two teams of eight players, it was initially dubbed “octopush.” That name is still in use in some countries, though since the size of the teams was reduced, the numerical basis of the pun has been undermined.

What began as a recreational diversion for sub-aqua enthusiasts soon gained worldwide popularity. We’ve seen before in this column what happens when a game conceived for fun morphs into a global sport. A governing body is set up, new rules are drawn up, people throw tantrums.

In the case of underwater hockey, the drama under the water has been more than matched by administrative theatrics. Disagreements over the 2006 World Championship briefly resulted in two rival governing bodies claiming dominion over the sport. Unity seems to have been restored under the umbrella of the World Underwater Federation (aka CMAS), with the 2013 World Championship taking place in Hungary this month.

Thanks to the success of underwater hockey, intrepid pioneers experimented with sub-aquatic variations of other popular terrestrial sports. Both football and rugby have been given the elemental makeover.

Underwater rugby, also governed by the CMAS, is much more rough-and-tumble than underwater hockey and makes full use of the 3D spatial possibilities offered by a swimming pool. The competing teams vie to get a saltwater-filled ball into baskets positioned on the floor at each end of the pool. Defenders often drape themselves over the top of the basket while attackers try to haul them out of the way. Scoring often comes down to who can hold their breath the longest.

The same physical challenge faces the underwater hockey players in Slovenia. The game ebbs and flows. Each score is transmitted after the event when the surfacing players raise their arms triumphantly.

Exhausted individuals are substituted. The understudies waddle in their flippers to the poolside. I don’t envy them as they stand there apprehensively, filling their lungs, preparing to take the plunge.