Researching dive/scuba options
First, I investigated all PADI instructors on Oahu. The costs generally range from $250-$500 for 3-7 day classes. The best deals I found were $249 for a 4 day course and $275 for a 3 day course, both of which include all fees and gear rental in that price. This is good because I don't have to invest in buying my own equipment just to learn the sport.
Second, I looked into options for diving through my employer, NOAA. As it turns out, the NOAA Dive Center in Seattle offers free training for NOAA employees. The result is a "Working Diver" certification, which allows one to perform almost any underwater work for scientific, government, commercial, or military purposes. The course is 3 weeks long and is offered during May and September. I'm in the process of trying to convince my supervisor to let me go (and pay my travel and lodging). I'll post an update when I have one.
As it turns out, the local NOAA dive unit in Hawaii doesn't need any more divers at this time, so we can't justify the expense of training me through the NOAA program. Thus, I'll go back to my original plan of earning my PADI open water certification and will try to accumulate some dive experience on my own.