Undergarments for the short term?

[Outbound]

The suit I have on order is a Fusion Sport aircore. I have some under armor like base layer, some merino long underwear and a polyester pair of thermals that have a fleece like inner surface.

I will buy some 4th element or similar (or get for Christmas) but I’m just trying to get 1-2 dives in the next month or so. The coldest temp will be on my aow deep dive where temps hold in the mid to upper 40’s year round.

Depending on what you have already and what you still need to buy, you might want to consider something like the Aqualung MK2 fleece suit. Price out the difference and see if it's worth investing a lot in base layers rather than just putting that money towards a drysuit garment that will serve you better. I used the MK2 until recently, when I got a Thermal Fusion. No doubt about it - the Thermal Fusion is a LOT warmer. But, with the base layers I already had from other activities, using the MK2 was fine, and I regularly dove water temps down to the mid-40s with it (and one dive at 35 degrees). The Thermal Fusion is nicer for long quarry days, especially late or early in the season when I'm doing 5 dives a day in cold water. But the MK2 with some merino wool or good polypro base layers under it also works, and I used it through early-December last year here in Michigan.