SDD - you ride a cage attached to a bar the length of the tank. Your depth is barely below the surface and you stand there and get 'driven' from one end to the other.
DQ - is a regular SCUBA dive in the tank. The first part of the dive was a bit more supervised, you went in the bubble and stuff, but after that you and your dive buddy just did your own thing, having the entire tank to explore. You feel like you become part of the attachion...which is how the CM's explained it..... But you do have to be a certified diver... About the sharks.....well, it was explained that if a shark was coming right at you, it was a good idea to get out of the way but being well fed I'm aware of no incidents in the 10 or more years they've run this... No standing in a cage here. Still a highlight in my divelog.
p.s. DQ costs less & does not require park admission....if the family is in the park and identifies themselves to a CM, they will be escorted to a viewing area (aka legal line jumping). We have cool video we took; & waving at the folks in the rest'raunt is FUN....
BUT you need an open water C-Card....