No F-18s in my future...but I did fly OH-58s in the Army. I was an aeroscout...cool gig.
When I say foot pocket fins I'm talking more about ones like this:
They are not quite the same as the ones I use at the Y, the ones shown are much nicer. The ones shown in the first link are likely to be the updated Zoomer fins. My Zoomers are red and look like foot pocket fins cut off just forward of the toes. Great for swim drills but no enough thrust for the hypoxic swims.
The second link is for the Finis swimmer's snorkle for freestyle swimming. It is designed for freestyle swimming and works perfectly for that. The funny bend of the air tube runs over the top center of your head a bit and because of the shape is easier to clear. The mouthpiece is the thing on the bottom and it has no purge valve. That funny looking thing in the middle is the head strap. Weird picture.
I don't do the butterfly so I don't know how deeply you shove your head into the water during the stroke. If your head goes more than a few inches under the surface you will likely fill the snorkle and have to clear it each time you come back out. Probably easier to go without.
This is a great tool for practicing freestyle, more accurately the crawl, because it allows you to concentrate on the underwater components of your stroke and watch your hand entry and stroke path.