On a recent sunny afternoon, Will White ventured into Peter’s Memorial Woods in Clinton, holding a global positioning system receiver and intent on the pursuit of treasure.

Of course, treasure is in the eye of the beholder. In this case, the booty would be a plastic box containing a log book and a few small trinkets.

It’s the thrill of the hunt that calls White, his friend Bob Kyrcz and their families, all of Madison, to trek through the woods in search of the coordinates where their prize can be found.

The Whites and Kyrczs are geocachers — part of an increasing number of enthusiasts who are taking part in what some call a game, others a sport, and still more know simply as an obsession.

Geocaching (pronounced geo-cashing) is a GPS activity where users share coordinates and hunt for hidden “caches,” boxes filled with goodies, all over the world.

Geocachers meet on the Internet to gather new coordinates, and have formed a tight-knit, worldwide community of hunters.

They have their own lingo, etiquette and codes.

Geocachers even borrow from Harry Potter author J.K. Rowling’s term for nonwizards in nicknaming those who don’t know about geocaching: “muggles.”

“If you look for geocaches, you’re not supposed to let muggles know you are doing it,” White said.

But now, muggles are harder to come by. 

The portal to the world of geocaching is, for many, www.geocaching.com, the main site for posting and sharing coordinates and organizing geocaching activities.

Two Web site developers in the Pacific Northwest started the game in 2000 when GPS devices increased in both availability and accuracy.

In 2001, there were nearly 3,000 caches around the world, and 17 in New Haven.

“There’s like seventeen a day that come out now,” said Leslie Laing, a geocacher from Ansonia.

There are 4,505 caches listed in the New Haven area — which extends across the state — in nearby places like from Yale’s David S. Ingalls Rink, to Sleeping Giant State Park and to Pole Hill Park in Bethany.

Approximately 500,000 caches now exist worldwide. There are even 25 in Antarctica.

The Kyrcz family found caches during a family vacation to Hawaii.

“It’s the challenge,” Teresa Gallagher of Shelton, said of the game’s allure. “It’s the fun of ‘Oh, here it is.’ It’s a real odd ball thing, you either like it or you don’t.”

For locals who like it, there’s the Connecticut Caching Community, where geocachers meet to post and share stories — funny ones about makeshift “Lover’s Lanes” they’ve unintentionally come upon in the woods, sadder tales about “muggled” caches with ransomed contents.

“What’s great about Connecticut is there a very small community of folks so we tend to go out in groups,” said Kerry Wills, of Southington, who caches with his twin brother, Randy.

Wills, a Connecticut Caching Community moderator, geocaches two to three times a week, and will reach 1,000 finds in October, he said.

It is a game that appeals to people like Wills, an experienced hiker who has traversed Mount Kilimanjaro, as well as players like Jennie Miklautsch, who geocaches with her three young children.

Miklautsch, of Greenwich, took her daughter Maggie, 1, on her first geocaching adventure when the baby was just 6 weeks old.

Hunts are starred, ranging from one star for “park and grab” type finds to five-star treks that can involve scaling rock walls or traveling by boat, Miklautsch said.

The varying degree of difficulty allowed Miklautsch to geocache up until six days before Maggie’s birth, she said.

Now, she and husband, Bob, Maggie, and sons Ryan, 5, and Ethan, 2, have logged 630 caches.

“The kids really love it, they love to be out and about, my five year old loves to find them,” she said.

But geocaching isn’t all fun and games, said Gallagher, a conservation agent and geocacher.

If caches aren’t hidden appropriately, sites can be damaged by overzealous seekers ripping up vegetation or stone walls to search for caches, she said.

She said additional clues on the coordinates and practiced etiquette of participants can help preserve both nature and geocaching.

“Every so often there seems to be another state that is banning (caches in parks)… they can cause some problems if they’re not (properly) done,” she said.

Leslie Laing of Ansonia, who has been geocaching since 2002, said most geocachers are conscientious.

She uses the treasure hunts as educational opportunities for her daughters, Amanda, 13 and Abby, 10.

“We pick up trash in the woods when we find it. They get to see what they learned in school, my daughter learned about vernal pools and she saw one first hand,” she said. “We identify animal tracks.”

For the Kyrcz and White families, their journey into the world of geocaching began when Jessie White, 8, and Sophia Kyrcz, 9, inadvertently stumbled over a cache at Hammonasset State Park in Madison two years ago.

Now they search all the time in places like Peter’s Memorial Woods — just 10 minutes from their home — that they had never before encountered.

“One of the fun things about this … it kind of brings us places we’d never know existed,” Bob Kyrcz said.

As his GPS indicated they had reached their destination, Ana Kyrcz, 12, pulled a box from between two trees, revealing a find made up of trinkets like WebKinz cards, a signed golf ball and a miniature skateboard.

Geocache etiquette allows those who find the cache to take some of the goods — if they replace them. The families did so with a lottery ticket, a marble and a patch.

“We (always) liked to hike, this just gives us a little purpose when we’re hiking,” Bob Kyrcz said.