The sharpie is an ingenious invention. I now sign all of my oil on canvas paintings with a sharpie, instead of trying to stumble around with a brush
with paint on it. And I can do this anywhere, upside down, underwater (as you mention) or if I painted on glass or human skin.
I think at this point I will exit this conversation.
Early erasable pens were really atrocious but they did improve. My mom had a stroke and would make a lot of mistakes when writing and always used an
erasable pen... really they weren't bad. They're still readily available.
While this may be sharpies first liquid graphite pencil, it's not the first. I picked up a couple of these (off brand) at Wlalmart a couple of years
ago. Really feels like a pencil when you're writing. My only issue was how quickly you go through the graphite and I never could find refills.