Rich Williamson and his girlfriend were talking about kids. Not necessarily whether they’d have them, but what sport their hypothetical offspring might play. “I don’t want my children to play football. It’s too violent,” the 38-year-old Alexandria, Va., resident decided. Baseball was deemed boring. And as for the world’s most popular pastime: “Soccer’s lame.”

It’s not that Williamson has never enjoyed playing those sports, or a slew of others, including lacrosse, basketball and rugby. But none has ever managed to be as awesome as a game he remembers from his elementary school days in Texas. It was like soccer, but you could pick up the ball and throw it. Williamson realized that if he could codify the rules, sprinkle in elements he enjoys from other sports and rustle up folks to play with him, he’d be a big winner.

There’d be the glory of being the founder of a sport, the fitness benefit of running around while punting and heaving and, of course, the gratitude of his descendants.

So he slapped together a Web site for his creation, dirty pool (www.dirtypool association.com), and invited members of Meetup.com to join the movement. Two weeks ago, when Washington, D.C., resident Greg Nelson, 32, stepped onto a field in Alexandria for the first game, he was ready to be part of history. “I’ve played a lot of sports — I think I’ve played every sport there is — but I’ve never invented one,” he said.

Time to get cracking then, huh? The instinct to make up sports is as old as humanity, and while we usually think only about the ones that get airtime on ESPN or result in Olympic medals, there are countless others. They might not have formal leagues or the fanciest equipment, but many of these sports have players who are just as passionate as any pro.

Just ask Michael Rosen, author of the new book “No Dribbling the Squid: Octopush, Shin Kicking, Elephant Polo and Other Oddball Sports” (Andrews McMeel), which catalogs some of the sports world’s more exotic offerings. There’s everything from bossaball, a variant of volleyball that encourages the use of feet (and includes trampolines), to chess boxing, which is exactly what it sounds like. “It’s the intersection between creativity and competition,” Rosen says.

He says the sports he writes about fall into two categories: ones created out of a sense of humor and others that come from people pushing the limits of the human body. “They think, ‘I can do this on two feet, but can I do it from a canoe or underwater?’” Rosen explains. Whatever the motivation, the ones that stick around satisfy our fundamental urges to hurl, throw and kick. “It’s a little more appealing than standing on an elliptical,” he adds.

Nelson, along with the other inaugural dirty pool players, isn’t so high on gym cardio. “I don’t do aimless running,” he told me as we walked toward Williamson, who was prepared for the occasion with a sack of size 3 soccer balls (small enough to easily grip in one hand), cones to mark zone lines and a stack of dirty pool cheat sheets with a first draft of the rules.