Go for the lake swim. Stay to the back or middle and outside and you won't have much contact to worry about. The first open water can be a nerve wracking experience, but once you realize that nothing bad is going to happen to you your nerves will calm down.

My problem, in my first tri, was with the lack of visibility in the lake and no experience with open water swimming. If you can get out a few times prior to your race it will be a big help with your confidence.

Try an open water swim first - some people can be quite uncomfortable when not able to see in the water like they can in a pool. If you feel comfortable then go for it.
Good advice to seed yourself to the back and away from the buoy line. Less congestion. Also waiting a few seconds after the wave starts to let the onrush go can save you some jostling around as well.
The other thing with doing a couple open water swims prior to the event is to practice sighting. First time out you may be surprised at how crooked you swim - when there isn't a nice black line to follow like in the pool - you constantly make corrections and swim straight - try and swim with your eyes closed in the your lane - not near the end (don't want to bang your head!) - and see if you end up swimming into the lane dividers.

This video should explain every you need to know about the swim...

http://www.youtube.com/watch?v=r3S0wu4Zbfk

My first (and so far only) tri had an open water swim. We went down and trained in the lake where it was going to be. My uncle was going to do it too, but when he went to train in the lake it freaked him out, so my mom ended up doing the swim portion for him. So go swim in a lake like you would in a tri and see what it's like.

As far as the open water start, I started more on the outside and didn't really have much problem with people piling on me or anything. My mom (who was in a later starting) said that it looked like a buncha fish flopping around on the inside. :P Oh and also. this one was not a mass start they started like two or three age groups at a time I think.

You are the first person to mention this and I have been wondering about the effect of the temp on performance. I won't have much opportunity to swim in open water before my first tri, but I am not anxious about it. However, I am concerned about the effect of the water temp. I am small (about 110 lbs), and I am wondering if I will be at a much greater disadvantage physically, OR is it just a question of mental toughness and I need get over the wimpy "oh it's so cold" factor. Thoughts?

Go for it. Don't hold back on the open water swim just because you think the experience might be a bit nerve wracking. It will be, but if you prepare yourself for a little contact, you will be OK. Keep your breathing under control. Assert yourself in the water (defensive swimming). And "sight" every 25-50 meters or so you will stay on track. As others have said, start in the middle and wide. You don't necessarily want to start in the back because then you'll have to swim over and around a lot of people. And prepare for the turns. This is where everyone bottle-necks. Good luck.

I did my first Tri in open water as well. I wasn't as freaked out about it as I thought I would be. I had never done an open water swim before, but I guess I just knew that no matter what happened to my time, I wasn't going to drown. I have always felt I was a strong swimmer (read: survival skills). I say go for the OWS. If you have time to practice before in Open water, all the better. The important part is that you be prepared to do this distance. If you are well prepared for the distance, you shouldn't have any problem 'making it' beyond the general chaos of the start rush. There are ways to avoid that which have been listed above, and all are great ideas. Just stay calm and you should be fine.

One last thing... if you do OWS, have a back-up plan. Mine was, If I get tired, I am going to roll over and kick on my back until I catch my breath. I found that the cold water was making me gasp for breath uncontrollably, so I was having a hard time getting a rhythm going. If you get yourself in a bind, remember that you can always float on your back, and just make sure you are kicking in the right direction...

Hehe..TryScott your post reminded me of an open water experience I had. it wasn't my first open-water tri (I think it may have been my 5th or so), but i hadn't done one in over a year. The race was a 1/2 IM in Illinois and so I showed up a day early and swam on the course to get a feel for water temp and such. I was so prepared there should have been no problem.

Turns out, nerves hit me for no apparent reason on race day. I started the swim my usual way, heading toward the outside to stay out of people's way. Adrenaline had my heart racing. Then, less than 100m in, I started having what I would say is the closest thing to a panic attack I've ever had. My heart was pumping so fast and whenever I had my head under the water I felt like I needed more air and I couldn't breathe...It was terrifying.

After contemplating DNFing at the start (pretty humiliating i'd imagine), I ended up swimming a modified freestyle where I kept my head above water the entire time for the first 500 until I calmed down. Needless to say, my swim time was nothing to brag about.

Just thought i'd throw that out there. BTW, this is not meant to scare you for open water swims if you're a noob. Probably not the best place to post this, lol.

That's pretty much my only mode in open water. Like that movie "Castaway" after his homemade raft breaks and the fish are coming up and gnawing on him and stuff.