This is so cool: small submarines with neutral buoyancy that literally fly through the water. Graham Hawkes has designed and built many of the small submersible vehicles used in undersea film making and exploration. His company (Hawkes Ocean Technologies) has extended this with "hydrobatic" vehicles and they have even offered a "flight school" for people wishing to become underwater pilots (only two classes so far, in 2003 and 2004, next one planned for late 2007-2008). There aren't many of these vehicles around yet, so the demand for pilots is perhaps a bit low right now. H.O.T. has built several prototypes and is seeking funding to build "Deep Flight II" which will be capable of dives to 36,000 FSW (feet of seawater), to the bottom of the Mariana's Trench!
Although I'm actually not much of a water person, as a kid I had a fantasy of building a personal submarine, designed around parts I could have ordered from the Sears catalog, which in the sixties carried a wider range of products than today. My mini-sub was based on a propane tank, various hardware, and a number of items from the boating section. It never made it off the drawing board, but it left me with a latent fascination for subs in general. As I think back now, the TV show Voyage to the Bottom of the Sea (1964-68) also played a pretty big part in this fantasy! In addition to the Seaview "mother ship," that show also featured a pretty nifty flying sub.
I found this (the real flying sub, not the old TV one) through a Flickr user and blogger (Steve Jurvetson) who does and photographs a lot of cool stuff. Some of his photos are in the Computer Simulations pool. Take a look at Steve's faves, rocketry pix, and adventures. I think I want his life.