Here, let me help you with that...

   O7
  /|
   Λ

That's ridiculous, nobody swims up a waterfall

(but actually, thanks for the illustration... my dad was in the military but apparently long enough ago that I entirely missed this)

Edit: oh! You used a capital O rather than a little one! That makes loads of difference... the "hand" placement in o7 is way over the forehead, while O7 (or is it 07? either way) is much closer to a proper salute! Perhaps the military culture hasn't entirely worn off after all...

It's also the wrong hand. But I think the little o looks more like a head in this case. O7 just looks like a hex code or something.

Right hand if you're standing behind him...

Ah... it makes sense. I thought it was a head being scratched.