Three months ago I couldn't swim 50 meters without feeling like I was going to heave up a lung, tonight I just got home from doing a 1000 meters without stopping 1200 all together. Watch Jimmy D'shea's video under freestyle (I don't think I spelled his name correctly) on youtube, that was very helpful to me. But the thing that helped me break through the endurance barrier the most was using a bouye between my legs so I could concentrate on technique and not worry so much about drowning and drinking pool water and doing this simple step series (each unit counts as a touch or 1/2 lap) 1,2,3,4,3,2,1. At the end of your endurance workout do some 25 meter sprints and monitor you time. I recomend doing at least 2 sprints. Finally swimming is about doing, make sure you are swimming at least 3 days a week and that you don't miss except for really compelling reasons. Then one day you will find yourself feeling like you can just keep going without stopping, when that day comes you will feel a wonderful sense of accomplishment and sort of at one the universe. For those of us who were never swimmers to begin with swimming is a real kick in the ***. Now I look forward to swimming workouts whereas before I dreaded it. The reason why there are so few triathletes relatively speaking is because people give up on what challenges them most thinking they will never overcome their weaknesses, I personally think swimming is the most challenging of the three to overcome if you have little prior experience. Good luck and just do it man!