Waterjet Propulsion? [Not just AIP anymore <g>]

[Coast Guard Kiteman <exfloridians@ecsu.campus.mci.net>]

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        Okay, here's ANOTHER topic that's been on my mind.  I haven't
had a chance to research this at all, so I'll put this to all of you.

        Is waterjet propulsion for a relatively *slow* moving object like
a personal submarine practical?  I know it's used on some speed
boats, and on "jet ski" type watercraft.  Seems like I've read or heard
that waterjet propulsion isn't practical for slower moving vehicles.

        It seems to me that a waterjet system would eliminate the 
problems [if any] associated with sealing a through-hull drive shaft 
turning a propeller.  It would also eliminate any dangers a spinning
prop would have on anyone swimming near the sub.