Tri Jersey while swimming?

Yes, tri top under the wetsuit.  

Definitely, learned this lesson the hard way. A 4 minute T1, most of it wrestling with my jersey!

x2!!  I tried not wearing my jersey under my wetsuit last month. Big mistake! Impossible to put on quickly when you're all wet.

Absolutely still wear it.

The pockets on a tri top are usually fairly well streamlined and will stick tight to the body when empty.  Any miniscule amount of drag created by them is FAR outweighed by the time saved in T1.

Of course, this is one reason to prefer something like the Orca Core tops over a 2XU top.... my Orca has a flap that covers the pocket so the water will flow right over it.  My 2XU has open pockets that seem to be perfectly placed on the sides to catch water as I roll, lol.  The 2XU top is fine for a wetsuit swim, but the Orca would be better in a non-wetsuit swim.

yes I wear mine while swimming. My first tri ever, I learned the hard way and didn't wear it. Wrestling in T1 trying to get it on was stupid.  I also learned after my second tri to skip the socks on the bike. Feet were so wet, almost impossible to get socks on easily. It does take a few races to start to figure out what to do and what to not do in transition. 

My 4th tri I learned something from the previous tri where I watched a guy come in and instead of backing is bike into the rack, he put it in going forward and had his running shoes under the back wheel.  That saves time as  you don't have all your stuff spread out under your front wheel.  I'm not certain about the amount of time saved (maybe a few seconds) but in a sprint a few seconds can make a big difference.

One caveat to not wearing the top in a non-wetsuit swim is the amount of drag it could prevent...

Not all triathletes wax their upper bodies. 

Probably TMI, but I bet I lose 10 seconds per hundred with all the hirsute ("hairsuit" as my kids call it) torso wet blanket effect. 

I do not like swimming in my tri top either.  But I don't like putting on wet so I use a speedsuit.  I believe it is the fastest non-wetsuit option for anything other than a short sprint.

pops, I'm curious.... how much benefit is there with a speedsuit, and does anyone know if they are legal at all races?   I have a HIM coming up that more likely than not will not be wetsuit legal, but if a speedsuit is legal and will provide a benefit, I'm interested.

They are probably about mid way between a wet suit and a non wetsuit. In my case, 1:17/100 avg wetsuit, 1:20/100 avg speed suit, 1:24/100 with neither (based on half and full IM splits over last two years).

Some are legal, some are not. It is about the material they are made from. The WTC has a list of banned and approved suits on their site.

Cool, thanks!

ETA:  I couldn't find the WTC list, but here is the USAT List

I bought a Blue Seventy ZP3 several years ago for Hawaii 70.3 and then had to buy a non-rubberized Xterra M when I went back several years later after the rules changed.  Some races have followed the WTC guidelines, some have not.  Both suits are pretty close in performance. 

I find them much quicker to remove than a wetsuit.

Yeah, but I'm also that guy who needs to use the bathroom at least once or twice in anything longer than OLY, so a one piece speedsuit would cause me problems in the using the porta potty area

A speedsuit is only worn over a tri suit during the swim and is removed in T1 just like a wetsuit.  Also referred to as a swimskin.