I know what you'll say, but hopefully you can assuage my fears and provide some advice.

There's a small tri being put on by a localish (not mine) university as part of its homecoming event. 1/4mi pool swim, 16-mile bike ride around the campus, 3.2-mile run. The bike leg should not be a problem, the run...well, I'm not really a runner, but if worst comes to worst I walk pretty fast. My concern is the swim. I haven't actually been in a pool much since I graduated from high school...while cardiovascularly, I'm in much better shape than I was then, I'm not entirely sure I can swim efficiently. Doggie-paddling a quarter-mile is probably not effective, is it? (Oh, and I may need to buy a swimsuit...)

My other major concerns are the transitions (there aren't really any details), since I don't own a pair of tri shorts (yet?) and the fact that this thing is in October. I really don't want to go out there with wet hair...
If nothing else, the tri falls on my birthday (10/22)--it's an excuse to eat a bit more cake than I should, right?