At 5:30 a.m. on the 12th, at Arena Plaza by Lotte World Tower in Jamsil, Songpa-gu, Seoul. It was early, but participants in the "2026 Lotte Aquathlon" warmed up as they waited for the start. Participants ranging from their teens to their 70s checked their gear with tense expressions, while families and friends held signs with cheering messages to encourage the athletes.
The Lotte Aquathlon held that day is an urban composite sports event consisting of swimming two laps (1.5 kilometers) of the east lake of Seokchon Lake, followed by a sky run up 2,917 stairs to the 123rd floor of Lotte World Tower. An aquathlon is an event derived from triathlon, also known as the Ironman race, that omits cycling and does swimming and running back to back.
Marking its fifth year, this event allows only registered athletes of the Korea Triathlon Federation to participate for safety. About 1,000 people took part, the most ever.
Cha In-taek, 79, the oldest participant in this year's event, said, "I came to conquer the grand stairs of Lotte World Tower."
Kim Pyeong-soon, 68, the oldest female participant, said, "I exercised six days a week and rested one day to manage my condition," adding, "Determined to compete this year, I asked my son for help and got registered as the 640th entrant."
The venue buzzed with energy even before the start. Participants wore swim caps color-coded under Korea Triathlon Federation standards and warmed up individually, and at 6 a.m. they received CPR training and did group stretching on the lawn plaza under the emcee's guidance. All around the venue, participants and families were seen taking commemorative photos.
Following the opening ceremony, at 6:50 a.m., participants set off on the Seokchon Lake swim course in groups according to their swim cap colors. Safety boats and rescue personnel were deployed throughout the course to prepare for contingencies. Some participants were seen taking a brief break midcourse before resuming the race.
After finishing the swim course, participants exited the lake, changed clothes, and headed straight to Lotte World Tower. Families and supporters chanted athletes' names at the stairwell entrance, cheering them to finish.
Around 8 a.m., the lead group completed the course and returned to Arena Plaza. A photo zone was set up to check results and take commemorative pictures, and a booth engraved each finisher's time on the medal.
The event was attended by Lotte Property & Development CEO Jang Jae-hoon, Songpa District Office Chief Seo Gang-seok, Korea Triathlon Federation President Maeng Ho-seung and others, who encouraged the participants. Jang said, "This event, where athletes swim in Seokchon Lake—which opens to the public just one day a year—and climb Lotte World Tower, the tallest building in Korea, has established itself as a distinctive sport symbolizing harmony between the environment and the city," adding, "What makes this year's event especially meaningful is that it reflects the results of the Seokchon Lake water quality improvement project carried out jointly by Lotte and the Songpa District Office."
Lotte has been pursuing a Seokchon Lake water quality improvement project with Songpa District since 2021. By applying an eco-friendly method using photocatalysts to reduce algal blooms and improve water quality, the lake received a Grade 1 rating in most categories under water environmental standards as of the 1st of last month.
There was also a water quality improvement demonstration that day. After all participants finished the swim course at 9 a.m., the water quality of Seokchon Lake was measured. A representative from GENKS, an environmental restoration and purification research company that has worked with the Songpa District Office on improving Seokchon Lake's water quality, explained, "The green container contains NanoGENS, which, when exposed to light, breaks down and suppresses algae, and the white container contains a polymer electrolyte that coagulates algae and particles to precipitate them." NanoGENS is a patented substance independently developed by GENKS to purify Seokchon Lake.
Lotte Property & Development operates a water purification vessel twice a week and administers chemicals to manage water quality as part of ongoing purification efforts. The company plans to continue improving Seokchon Lake's water quality and expanding eco-friendly activities, while increasing sports and cultural content for citizens to enjoy.