New Kid on the (Endurance) Block: Marunuma Swimrun

What is swimrun?

In short, a swimrun race is an endurance event combining varying distances of open water swimming and running.

Participants repeat varying distances of open water swimming and running, back and forth. Unlike an aquath(l)on, there are no transition points for changing or swapping gear. So, participants must bring all of the wear/gear that you start the race with to the finish line. 

Athlete looking into distance at Marunuma Swimrun

Originating in Sweden, swimrun has rapidly gained popularity in recent years and there are now over 200 races held worldwide.

In Japan, an introductory sprint distance swimrun was held in May 2017 in Tokushima. The inaugural race featuring both a standard and sprint distance was held in Marunuma (Gunma prefecture) in 2018. The second official race scheduled for late August will again be held in Marunuma.

swimrun FAQ

Swimrun is inherently an endurance sport repeating varying distances of open water swimming and running. While sounding similar to aquath(l)on, swimrun has no transitions, meaning participants run in a wetsuit and swim with shoes. The use of swim tools such as pullbuoys, paddles, and short fins are often permitted.

Solo races are uncommon; instead, swimrun usually involves two people (usually of similar abilities and speed) acting together as a team to start and finish together. Teams are often tethered together and must not separate more than 10m from one another during the race. 

  • Rules and restrictions may change from race to race; however, standard swimrun equipment guidelines are below.
  • Required Equipment: swimwear (often, a wetsuit is mandatory), fast-drying shoes with grip, bib, swim cap, and course map
  • Recommended Equipment: swim paddles, pull buoy, compass, waterproof bag, first aid kit, and rope for tether (so that teammates may not be separated by more than 10 meters),

You should practice running with a wetsuit, swimming while wearing shoes, and transitioning multiple times. It’s also a good idea to consider your race style and the devices you’re willing to carry – all equipment carried at the start must be carried without throughout the race.

Just as important is the practice of racing with another person – throughout the entire course! Before a race, practicing transitions together and being attached by a cord  is a key preparation for a swimrun race.

Surprise! There is no transition area for a change of clothes or holding/collection of equipment, including eye wear.

Throughout a swimrun race, athletes are continuously swimming and running. So if you wear shoes and a wet suit, you’ll be wearing shoes while you swim and a wet suit when you run. Of course, some teams opt to place their shoes in a waterproof bag for the swim because they can swim faster without shoes.

Experimenting with transition methods and practicing the most efficient transitions is something for swimrun teams to consider. 

The most common swimruns in the world range between 20 to 60KM. Sprints are usually no more than 20KM, while the longer ultra distances are often more than 50KM. 

Swimrun beginners are encouraged to join the sprint distance to first learn about the sport. While the percentage of swimming and running varies among races, you should be comfortable open water swimming 3KM (if not 5KM) at a minimum. 

Marunuma Swimrun

Participants of Marunuma Swimrun
Bay in Nikko National Park in Marunuma, Gunma

When: August 24-25, 2019

Where: Nikko National Park (Gunma Prefecture)

Distances: Standard Distance – 30KM total (swim: 8KM, run: 22KM) / Sprint Distance – 10KM (swim: 2.5KM, run: 7.5KM)

Standard: ¥52,000 (early entry: ¥48,000)
Sprint: ¥20,000 (early entry: ¥18,000)
* includes after-party

Registration Period: until July 31, 2019


August 24th (Saturday)
7:30am-8:30am Standard, Sprint packet collection, gear check
8:45am-9:30am Standard, Sprint race briefing
10:00am Standard, Sprint start
5:00pm Standard, Sprint COT
6:00pm Awards

August 25th (Sunday)
9:00am-9:30am Mini race packet collection, gear check
9:30am-9:45am Mini race briefing
10:00am Mini race start
12:00pm Mini race COT
1:00pm End of event

* tentative; subject to change without notification

Marunuma Swimrun Basics

2018 Inaugural Marunuma Swimrun