Surrounded by water as Mercer Island is, water sports have long had a strong foothold here. Rarely, though, does a new sport gain unprecedented traction based on an Island event. Stand-up paddle surfing is a hybrid of kayaking, surfing and, if not balanced correctly, swimming, which comes with a moniker befitting the surfing culture: SUP.

It may be a fairly new concept for the Pacific Northwest, but it’s growing rapidly. So fast, in fact, that this weekend will boast the largest SUP race in the Pacific Northwest, the ’Round the Rock race held on the Island at Luther Burbank Park on Sept. 27.

Jeff Underwood, an Island resident, and friend Dan Eberhardt, who lives in Manhattan Beach, Calif., but is from the Eastside, are longtime surfers and recent SUP enthusiasts who decided to organize a local race for the sport to benefit a local water charity.

At 8 a.m. on Sept. 27, paddlers will assemble at the Luther Burbank swimming beach to take off around the Island in the largest event that the sport has seen north of California. Underwood said that 80 racers have already signed up for the event and more are expected on the morning of the race. Later in the afternoon, the guys will host a “sprint” race, starting at the park and paddling to the East Channel Bridge and back for a 1.25-mile race.

The sport, like most branches of surfing, has origins from Hawaii, where Underwood first gave it a try and fell in love with the unique hybrid. Eberhardt, another longtime surfer who lives on the beach, said even though he surfs as much as he can, paddling offers a different take on one of his favorite pastimes.

“I tried it and immediately I was hooked,” he said. “I’m addicted.” Both have seen a huge groundswell of support for their race, highlighting the recent popularity of paddle boarding.

Months ago, Underwood said he would go out and paddle around the Island, or even in Puget Sound, and see maybe one or two paddle surfers cruising in the summer sunshine. Now they are everywhere. Boards can even be rented on Lake Union near Gas Works Park.

True to surfing standards, most paddlers in the area can be found on the ocean, catching ferry wakes and sometimes paddling between islands, but Underwood said surfers are only beginning to scratch the surface, paddling on inland waterways such as Lake Washington. The boards themselves are typically a little thicker and longer than traditional surfboards, but the style and length vary as much as the people on the water. Underwood said typically beginners will start out on a long board, as it gives more balance support, but for surfers who are well versed at getting up on their boards, a shorter version works just as well. There are also race boards which can help the paddlers reach five to seven miles per hour on the water.

“The boards were getting smaller and smaller, but now we’re seeing these long, light, fast boards made with new technology. They’re still trying to figure out what fits,” said Eberhardt. The SUP community, which remains fairly small, passes around information about what is working, and what isn’t, quickly.

Besides being another reason to get out on the water, rain or shine in their cases, Eberhardt and Underwood said SUP provides an amazing body workout while rewarding paddlers with views you can’t find anywhere else.

“I haven’t found anything that’s more of a total workout,” said Underwood. “The best thing about it is you don’t even realize you’re working out.” The balancing and paddling provides for a strong core workout, Eberhardt said.

What really gets them going is not the workout or the fact that they are cruising around on the water, but the chances to see the world of water from a fresh perspective.

“It’s a new way to experience being out on the water,” said Underwood. “It gives a new perspective, and you can see into the water. You can see the fish and sea life,” said Eberhardt. “I’ve been surfing for over 20 years, but you can’t have the same experience surfing you have out there. It’s a totally different deal.”

The idea for Paddle ’Round the Rock developed mostly because Underwood and Eberhardt were looking for another reason to paddle all the way around Mercer Island. Underwood said he rarely has enough time to make the complete loop, and once the race idea got underway, it took off; in a big way.

Proceeds from the race will benefit the Surfrider Foundation, an international nonprofit group which has chapters in Seattle and the South Sound. The local chapters will be using the money raised on Sept. 27 to set up Blue Water Task Force labs, which test water where people commonly recreate.

The race started off as a way for local paddlers to get out on the water, but has quickly become an event to showcase the sport, attracting industry booths, such as several of the big board manufacturing companies that will be providing information and examples. It is turning into a great way for people interested in learning about paddle surfing to come check out the sport, see demonstrations and give it a try, Underwood said.

While the race around the Island is scheduled for a 9 a.m. start, depending on the weather, Underwood said that people not participating are encouraged to come later in the morning to see the booths and talk with people in the industry. The fastest paddle surfers are expected to finish in about three hours. The race to the bridge and back will start at 1 p.m.

“There are other races in the area, but they have all been smaller. This is the biggest thing in the sport around here right now,” said Underwood. The duo expects ’Round the Rock to become an annual event.

“Based on the number of contestants and booths, this is the biggest thing north of California,” said Underwood.

For more information about the event, visit www.roundtherock.com.