I just got the 24 hour marathon DVD pack today and started watching it (due to someone bringing it up in the Mr Spock thread). I watched this show like crazy when I was a kid, and it's probably what injected me with the SCUBA bug at an early age.
It was fun watching it as a kid (from what I remember), but it's really fun watching it now. A really well done series and it's neat to see all the old time SCUBA gear in use. I didn't remember that the premise was him being a research diver, only his research included politically incorrect stuff like capturing animals for Marineland, testing spear guns, researching underwater mining, and working for oil companies. Not a single "save the whales" episode so far! 
It's almost an educational series, as Lloyd narrates in the background explaining a lot of dive physics and other stuff, which I also think is pretty cool.
Lloyd Bridges AKA "Mike Nelson" was an ex navy "frogman" or more properly refered to as "U.D.T." or "Underwater Demolitions Team" during the war, that being no doubt the Korean War. UDT derived from Naval NCDU of WW2 and would eventually be the genesis of today's Navy SEALs.
As a kid this was VERY intersting to me, watching that old show (though it was still fairly new back then) as my father had been in a UDT team during the Korean War. He would often watch the show with me, critiqing it, telling me what they did right and what they did that, had divers REALLY done that, would have killed them.
My father had three items he brought back from his Korean War service; an M-1 carbine (which I now own), a compressed Ccarbon dioxide powered spear gun, and his scuba tank.
Unlike the one Bridges' used, my father's had only one large sized steel tank with canvas webbing. A pull-ring ran down one side attached to a lever on the side of the unit; when pulled this activated an "emergency supply" `` actually it adjusted a valve allowing what little compressed air in the tank to give the user maybe five minutes of breathing time. The regulator was of the same type shown in that old show, a large disc-like assembly of metal that fitted to a valve on top of the tank. Over the right shoulder a corrugated rubber hose fed air to the diver, who upon breathing it, returned it through the left hose where it was simply dumped into the ocean through the regulator. In fact this served no real function and when the system was revised, the regulator was made smaller and part of the mouthpiece, and it expelled used air through a small assembly that simply kept it out of the diver's face.
My father's unit became rather bedraggled as it aged. My last memory of seeing it, the rubber hose had degenerated was gone. I don't know what he did with either the regulator, the tank, or the speargun. Perhaps he disposed of it when we moved.... Thankfully he kept the M-1 carbine, which survived the decades in
far better condition.
