Swim
The swim section of a Triathlon can take place in a pool, river, lake or the sea. If the swim takes place in an outdoor setting it may be necessary to wear a wetsuit. For many people the swim section of a Triathlon can be the most daunting, but you’ll discover that many competitors used their first Triathlon as a great excuse to learn how to swim properly for the first time in their lives!
Swim Bike Run
Bike
The cycling stage proceeds around a marked course, typically on public roads. In many cases, especially smaller triathlons, roads are not generally closed to vehicles; however, traffic coordinators are often present to help control traffic. Typically, the cycling stage finishes back at the same transition area. Racers enter the transition area, rack their bicycles, and quickly change into running shoes before heading out for the final stage
Run
You can walk during the running portion of a triathlon, but please don't "crawl." The rules don't explicitly mention piggyback rides, but those are probably covered in the clause forbidding "unauthorized assistance."
Since the running portion comes directly after the biking section, don't forget to take off your helmet. Running with a bike helmet is grounds for immediate disqualification. So is running without a shirt. And even though barefoot running is all the rage, triathletes must wear shoes at all times during the running portion and must also leave their iPods and mobile phones at home. Breaking any of these rules can lead to disqualification.
Sprint
These short distance Triathlons are the most variable of all the tri distances. These are usually the first step into triathlon for most people. the most common distances are Swim (750m), Bike (20km), Run (5km)
Olympic
The Olympic distance (also known as ‘international’, ‘standard’ or ‘short course’ distance) is one of the most common types of triathlon. The distances involved are very specific. They are: swim (1.5km), bike (40km), run (10km).
Half
A ‘half’ triathlon is half the standard Ironman distance. It’s often referred to as a 70.3 tri as this is the total distance covered (in miles). The distances are: swim (1.93 km), bike (90 km), run (21.09km)
Full
A ‘full’ or Ironman distance triathlon is often the ultimate goal of a triathlete. The distances are: swim (3.86km), bike (180km) and run (42.2km, Marathon).