I'm always cold, too. Came back from Roatan last month where the water was 80-81 and I was cold after 20 minutes in a full (pretty new) Henderson 3mm with a dive skin under and boots. I get chilly in 83-degree water after about 40 minutes in the same set up. I can't easily wear a hood because my face is small so my mask will leak (sometimes it does if I don't get it on just right even without a hood). So I'm considering buying a heated shirt (e.g. Thermalution) for future dives as we're headed to Fiji in May where the temps (according to the resort website) are around 77-78. I don't really want to go to a 5mm or thicker because I don't want to have to add a lot of weight (when I'm in good shape I only need 8 lbs but obviously I'm out of shape because I needed 11 lbs in Roatan :/). I think I'll probably always want the heated shirt, even when I'm in 83 degree water. For those that have one, does that sound like a good plan? Will it keep me warm enough?