Base layer for Aqualung Thermal Fusion?

[Mr. Dooley]

I've been diving the Fourth Element Arctics with a thermal underwear base layer (fleece-lined polyester blend). Certainly divable in the cold waters I frequent (52 - 55F), but definitely start to get chilly on colder dives. I've dived this down to 41F and it (unsurprisingly) was basically a cold endurance challenge after several minutes.

Recently upgraded to the Aqualung Thermal Fusion, which I was told would be a bit warmer than the Arctics (fingers crossed). Figure I may as well get a solid base layer also, the idea being you can't really be too warm when cold water diving.

For base layers, sounds like merino wool is pretty hard to beat. I've never owned anything of this material. Sounds like 250g is a popular weight for diving. But I also see heavier base layers in 400g weight - curious if anyone has any experience with that? Is 400g overkill or too buoyant / bulky to be practical?

I'm hoping even the midweight merino products + the Thermal Fusion will be a significant step up from my current setup of the Arctics + no-brand polyester undergarments, but I'm curious what other folks have experienced.

 

[runsongas]

something like a sharkskin/lavacore would be better as it would add less ballast required. 400g undergarment requires quite a bit of extra weight and between the 400g and a thermal fusion, you might need close to 40lbs of ballast to sink. a thinner wool undergarment would be possible if needed (like 100g to 200g similar to the mk1 undergarment), but would try just your current base layer with the thermal fusion first.