Non-Triathlon Wetsuits

Surfing wetsuits are hard to swim in because they don't have the flexibility in the shoulders. They are meant to be rubbed against the board so the outer fabric is not hydrodynamic at all. You can swim in these, but if you have no intention of going surfing it's a waste of money in my opinion. Often you can rent suits for a weekend for the race.

Cheers, Erik

WTC (Ironman brand) banned wetsuits thicker than 5mm in 2011, and the USAT rule goes into effect in 2013.  Most tri wetsuits on the market already comply.

I did my first tri in a surfing wetsuit I borrowed from a friend.  I was going to set any speed records and it worked just fine for newb like I was

I stepped up to a tri wet suit for my second, third, fourth etc...  and it does make a HUGE! difference but dang they if they aren't expensive.  

Tri suit is by far the best suit for swimming in, but you can absolutely swim in a surfing wetsuit.  However, it will make you slower and not faster.  The biggest issue is they are a little spongy so they tend to soak up water and gradually get heavier throughout your swim.  I rented one last year and my swim for an Oly was almost 5 minutes slower and my arms were pretty heavy towards the end so I felt a lot more fatigued in general.  But, it was 65 degrees in the water and it kept me very warm so I'd do it again in a heart beat.  In my experience i didn't have any flexibility issues because the entire suit is made of very flexible materials and was only 2mm thick in the shoulders.

So, if its a cold swim that you couldn't swim in without a wetsuit then surf suit gets the job done.  If it's merely wetsuit legal and you're trying to improve your performance then absolutely do not wear a surf wetsuit.  

All that being said, its best to save up for one of the xterra wetsuits.  I think they're around the mid 100's with the BT coupon code and they keep you warm and make you swim quite a bit faster.