Dear ladies, especially bony/skinny ones:
I am preparing for a 1.5 - 2 hour lake swim in circa 72 degree water (air temp 60 - 68). I do NOT like cold. I am total skin/bones from the waist up and get cold easy. I did an OLY recently without my wetsuit in 73 deg water (80 deg air) and by 20 minutes in I was starting to shiver.
My question is, have you ever overheated in your full suit on a long swim? What was the water/air temp when that happened?
Yes, when the water was close to the 78 degree wetsuit legal limit at Ironman Buffalo Springs 70.3 in Lubbock, Texas. Otherwise, I have been happy to have my wetsuit on when swimming long distance.
I agree that the 76-78 degree point gets too warm for a full suit for me.
Jodi
I’ve swum in my wet suit up to 78F and yes it gets a bit warm at that point - the 76-78F range is where it gets a bit too warm depending on the distance and level of effort.
I have overheated. Once it gets to be around 74 and up, I go sleeveless. I have a thin upper body, but wouldn’t describe myself as ‘bony’.
Do you have the ability to test out stuff a bit more before your swim?
Thank you SallyShortyPnts, Jodi, and f_ahsile04 for your answers above.
determination - I will have limited ability to test beforehand. I have a Desoto T1 two piece, with a long sleeve top and bib john. Theoretically I could just wear the bib john, and I might try that, but afraid it will turn into a parachute. Maybe I can hack a contraption to keep the top of the bib john snug around my midsection (duck tape?) . Water temp will be max 75, and that is measured near the shore - I expect the middle of the lake to be cooler. I will do the swim first thing in the morning, when the air temp will be 68 or less. I really have zero fat from the waist up on me, which is why I am concerned.
Thank you for all the helpful info.
Given how easily you get cold, it sounds like you’ll be fine with your full two-piece, but if you’re concerned, how about swimming with only the top of your DeSoto and not the bottom? It’s your upper body that is prone to getting cold, so maybe cover the upper half and just wear a swimsuit on your lower half? The only downside of that will be body positioning; you’ll have to work that much harder to keep your legs up relative to your chest. But you won’t have to worry about drag from the suit, and your upper body will definitely be warm.
I’ve regularly done 3-4k swims in my full wetsuit at around that temperature and been pretty comfortable.
Needs to be around that temperature before I contemplate not wearing my neoprene cap… I don’t carry a lot of in-built insulation either 
Thank you all for your input, ladies.
The swim got postponed a few times, and was actually held today, in quite toasty conditions, the lake was around 74-75 I guess. I wore my full suit and was comfortable for the most part. The neck felt a bit chafed the first 2K (I did use vaseline), but then it was not a problem after all. The top felt comfy, and had plenty fresh water coming in around the neck when I bent my head to keep me from overheating. I have now swam in this suit (DeSoto T1 two piece) a few times, and feel that the bib john is a bit too warm for anything over around 71F, and for me, also the 5mm neoprene floats my legs too high. My swim time was 1hr48 min for the 5.2K distance, and my low back really started to ache the last 2K or so. So for shorter swims in 72-73 deg water, I might just wear the top in the future (I am not much faster with the bib john on.)