Most people can ride a bike, and many people can jog or run a few miles, but the swim is a challenge and puts triathlon out of reach for some. I use the Total Immersion swimming technique to get every bit of distance per stroke and stroke efficiency in my triathlon training. The Total Immersion site has a lot of free information and products to help you with this stroke technique. I was able to reduce my strokes per length of the pool from 20 to 12 using this technique, making open water swimming much easier for me.

Above, I am finishing the 4K (2.5 mile) distance at an open water race on Bermuda.
Triathlon events from shortest distance to longest are: Sprint, Olympic, Half-Ironman, and Ironman distance.
This newbie site lists the various distances involved in the SWIM, BIKE, and RUN for each triathlon event and has resources for the beginner triathlete.
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