Going back a bit (I'm commenting mainly because I'm quite annoyed but I think I've got something useful to add) about cold water tolerance. I don't just dive, but also freedive, and in fact for me, freediving came first. I'd never choose to dive in a wetsuit in a million years, but I'd never dream of freediving in a drysuit. It's all about the right tool for the job for me at least. As great as theoretical knowledge is, it's the practical knowledge that really counts, as you think "ahh fuck that's cold" whilst you're floating about doing not very much at 30m - even in a drysuit. Diving makes you cold, swimming makes you warm, use a drysuit or learn to dive in Malta. This isn't just about comfort, it's about safety.