I guess the best three whoppers I've ever heard come from the dive industry, not from divers.
"Them J-valves will kill you, that's why we don't use them anymore."
Um, no, the USN, NOAA, and OSHA actually approve them as redundant air sources and REQUIRE them in some conditions. But the dive industry knows better. And DAN notes that somehow, even with pressure gauges, divers are still dying from "out of air" situations because they just forget to look at the gauge. The USN knows that even in black water diving, you don't need to see squat in order for the J "reminder" to work.
"You can't get a plus certification on your tank after it was made."
Um, no, the DOT says a + rating can be given forever, at every hydro, if the hydro shop knows what they are doing and the tank passes the test. But of course, that would mean "choices" and interrupt the assembly-line routine. And maybe, even require looking up numbers.
"You need a hydro and a VIP"
Um, no, again. The DOT says every hydro STARTS with a comprehensive VIP. If you got a hydro, you already got a VIP, there's no need for the dive shop to do a second one. When the dive shop says "Yeah, but they don't know how to do a SCUBA VIP" ask them, "So, the hydro shop is incompetent, but you used them anyway?"
There's enough FUD in the industry to go around, even if the divers remain speechless.