Measuring the Ironman Swim Course

One of the world’s most competitive and enjoyable short-distance ocean swims is the Waikiki Roughwater Swim, now on its 40th year. Traditionally held in September, the 2.4-mile Swim, starts at one end of Waikiki Beach, under the foot of Diamond Head Volcano, and finishes at the other end at the Hilton Hawaiian Village.

Swimmers swim over beautiful coral beds and colorful marine life in a picturesque course. Swimmers may also face high surf and strong currents depending on the conditions on race day.

The Waikiki Roughwater Swim is also the inspiration behind the 2.4-mile swim leg of the Ironman Triathlon. The event has grown from 36 participants in 1970 to a highly competitive swim that annually attracts over a thousand competitors of all ages and backgrounds from dozens of countries and across U.S.

Jim Anderson, one of the key members in helping develop and promote the Waikiki Roughwater Swim over the years and founder of the Double Roughwater Swim, gives us an overview of how the famous course is measured:

"The Waikiki Roughwater Swim course is not measured annually. It was originally measured by triangulation by a surveyor in the 1970's and I re-measured it in the late 1980's using triangulation by the U.S. Coast Guard from their tender on the course when they set the anchors at the turn points and mid-course."

"The accuracy of those points was re-done in 1999 using GPS when I created the 25K course for the USA Swimming National Open Water Championships. But, I am sure that today's GPS systems are better."

"There is no other practical way to measure the Waikiki Roughwater Swim course other than GPS. Even with the accuracy of today’s hand held GPS you would not have a pool kind of measurement given the problem of movement of the boat in which the reading is taken and its real relationship to the anchor on the sea floor."

But, for the tens of thousands of people who have competed in the Waikiki Roughwater Swim since its start in 1970 and for the thousands of others who train for the 2.4-mile swim leg of the Ironman Triathlon, Jim and his colleagues have set an iconic standard distance known around the open water swimming and triathlon world.

Photo of Waikiki Roughwater Swim start by Craig Kojima.