If you're about to do "discover Scuba Diving", rather than "Discover Scuba", then (if my understanding is correct and not outdated), your first try will probably be in the shallow end of a heated pool. You put on the gear and get used to being able to breathe underwater. Then, maybe how to float neutral underwater. I encourage you to try it this way rather than in a cold quarry, for your first experience with scuba.
Many shops offer that first dip for free, my LDS does it twice in fall and twice in spring, at the Tulane sports complex pool. That's how I started, though it was in a pool in Florida on vacation, followed by a 25' dive that weekend by the Palm Beach breakwater, with the same instructors. Then I was hooked. But, I didn't have that fear of a panic attack.
Your other sports tend to convince this bystander that you don't actually scare all that easily, once you get familiar with the sport you are undertaking. So try it in warm shallow water first, if you can. Then warm deeper water (the deep end of the same pool will work, especially if you can find one that's 10-12' at the deep end rather than just 6). Do a few fin pivots, get used to adjusting your buouyancy compensator jacket so you are "weightless" at a given depth, and notice how your inhales bring you up a little, and your exhales, down a little. Then you'll be more willing to try all this in colder water, I would think.
And don't let that bulky constricting feeling that dive gear, wet suit, weight belt, and mask can give you before you enter the water, panic or discourage you--once you get under, and get neutral, all that goes away and it's just mahhhvelous....
Where did you get this idea DSD is done the way you described? Maybe in tropical places, but it seems it's much more commonly done in a pool (maybe a shop's on site pool, maybe a lane a shop rents at a community pool). Free?
Weight belt, wet suit? If the DSD is done in a pool it will most likely be a jacket BC over her bathing suit.