This is what I was looking for. While I'm mainly a tropical diver, that 3+ day of diving I start getting chills. Might just invest in one of these.
Boatcoat/surf-fur is a good idea because we need to stay warm between dives too. I always bring extra layers of protection, even in tropical waters. I have a 1 mm beanie, sometimes I layer that over a 1mm Scap and I have a 3mm bibbed hood too, which I rarely have to use, thank heavens. I also have a Bare Chillguard, which is neutral to wear under my suit. And when I'm really suffering, I cover all up with my Sharkskin.
I have a 5mm that I'd never had to wear before, not even in the Red Sea in the month of November.
Yet, I went to Bali without it. Thank heavens I had all that other Headwear and the Chillguard and the Sharkskin. Brrrrr
Being cold on the boat was not an issue. The water was surprisingly, startlingly cold!