Ironman tri suits

Tri hard with vengeance

Hello all, 

I have been off the triathlon scene for about 10 years having been focusing adventure racing and ultra runs. I have particularly enjoyed the advances that have been made in kit in that time, as will my credit card. I recently signed up to do an ironman later this year. 

I watched some videos on YouTube of the recent world championships in Kona, and to my surprise the pros and a lot of the age groupers seem to start the swim in different tri suits then they end up cycling and running in. Surprisingly the transitions don't make for very entertaining highlights so I was wondering if someone is able to give me some insight as to what strategies are being undertaken, etc. Also how does this change when wetsuits are involved, if at all?

Thanks in advance.