I do it most years and don't recall seeing anyone in wetsuits.
The first year I did it, I was expecting more of a race-type event. (Not an all-out race, but more of a focused effort.) This thing is really social though .. lots of people of all ages, shapes, sizes and fitness levels and lots of breast stroke at a relaxed pace as people chat their way across the lake. Crawling is actually a bit of a challenge until you can find some open water. The chatting-your-way-across approach isn't a bad thing, as it's a cool place to have a conversation and the mountain and city views from the lake are outstanding. I still use crawl instead of breast stroke and save the chat for the end, but I go into it expecting to wait on people, get caught in some traffic and also take time to enjoy the scenery instead of making a heads-down charge for the opposite shore.