What is this muscle called?

I have the ability to close my nose off by closing some muscle, or something, that is at the back of my nasal cavity, above the soft palate. When I swim I close it so that water doesn’t get into my sinus cavity.

It has the added benefit of blocking smells when I want, which is why I have no problem changing the nastiest of diapers or using the most disgusting outhouses or whatever.

My dad “taught” me how to do this when I was very young and learning to swim. However, I can’t imagine how he taught me since it’s not anything you can see, but I can’t imagine not being able to do it.

The few times I’ve even mentioned it to others, I get a totally blank look. Due to a recent question regarding swimming, I’ve started trying to define this “ability” to others.

The main thing is, I’m pretty sure we all do it when we swallow. It’s just something we do subconsciously, and my dad somehow taught me to do it consciously.

When you take a drink, when you swallow, try to isolate what happens there, right above your soft palate, right where the bony nasal opening is. I know we use our tongue, too, and in fact, the back of the tongue pushes on that muscle when we swallow, but then try to relax your tongue without relaxing those muscles above it…..