Do NOT let the swim keep you from entering this event. Don't worry about it. I mean, get in the pool at least 2-3 times/week, but don't worry about your speed, etc. You will survive the swim. Repeat after me: You will survive the swim. It may not be pretty, it may not be fast, it may be tediously painful at times, but you will survive the swim.

Then you'll kick some serious butt on the bike.