Hundreds of people from around the Maritimes and beyond are spending the weekend looking under rocks and behind trees in the Fredericton area as part of the largest-ever geocaching event in the region.

More than 600 people registered for Maritime Mega II, which organizers say was on track to be larger than a similar event in Nova Scotia in 2010.

Organizer Nathalie LeBlanc said it’s a reflection of the sport’s growing popularity.

"We've got families that do it with really young kids, from babies and toddlers up," she said. "It's something that's also great for adults, teenagers, the retired community as well. There's quite a variety."

In geocaching, participants use GPS devices to zero in on the locations of caches by downloading their coordinates. The caches contain small containers that hold trinkets, tags or other items placed there previously by other participants.

Those who find the caches are expected to log the find. They can take the item if they replace it with a similar object. Some items have ID numbers that are registered online, allowing the people who hid them to follow their movements.

LeBlanc said the price of GPS units have dropped, making the sport more accessible.

"In recent years they've gotten a lot more affordable," she said. "You can buy one for right around $100."

Liz Keddy of Aylesford, N.S. said she planned her summer vacation around Maritime Mega II. During the school year, Keddy teaches in Qatar, in the Middle East, where she geocaches in the desert.

"There’s actually trees to find the [caches] in," she said.

Most of the participants in Fredericton are from the Maritimes, though there are many from Quebec, Ontario and the American northeast. Some came from Europe and one person was registered from Alaska.

Geocaching is also popular among retired people, like Sherill Minns of Riverview.

"It's wonderful when you're retired," she said. "You can spend your day on the bike trails on your bike and head off to find caches. It's excellent."

She and other members of a Moncton-area geocaching group recently completed a bicycle trip from Caraquet to Shippagan where they found more than 100 caches.

"When you find the cache, you get an adrenalin rush," she said. "This little shiver goes through you."