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.