It was a “Watch Cap” when issued to me in boot camp in October 1965. It was still a watch cap when I retired from the USN in 1993. And although I have lesser need since moving to Florida seven years ago, it’s still a ‘watch cap’ when I use it to keep my bald head warm.
That docker looks like a nice heavy hat. Aside from warmth another thing to consider is how tightly the cap fits.
I was on tug/barge anchored inside the spit at Dutch Harbor one time when we parted a head line. I put up the ladder to get up on the barge but as the wind pulled the barge away from tug the distance between the tug and barge was slowly increasing. I could see I had enough time to easily make it onto the barge before the ladder fell in but I was about two thirds the way there when a gust of wind hit and blew my cap off.
Something about having your cap blow off, the reflex is to grab for it but I also wanted to stay focused on getting up the ladder.
My dad who was a WW II mariner and later a USCG sailor gave me his watch cap when I was 12. I remember asking him why it was called a cap because it had no bill like a baseball cap. He said sailors don’t play ball they wear caps to keep their head warm. Which made absolutely no sense to me at the time but was indicative of his personality.
I’m not a brand snob at all, but the Carhartt watch cap is the only way to go. That’s what I see almost everyone wearing here in the Northeast. It’s pretty much a staple of anyone working in skilled trades, living in a rural area, or working in marine industry. They might call it a wool knit cap or something like that, but I use the term watch cap.
I’ve always thought of a beanie as somewhat different and distinct from a watch-cap. Though still a knitted hat, like a watch cap, I’ve always understood a beanie to be more large and baggie. I guess I always thought it was called a beanie because of the way it resembled a bean-bag chair. I see this as being separate and unique from the more form-fitting watch cap that sits quite close to the hair/scalp.