A few questions first...
1) Are you EXTREMELY comfortable with absolute zero vis diving? Most of your "searching" will be by feel alone (unless you count "taste"...experienced body recovery divers have said they can taste the corpse before they come into contact with it).
2) Are you very comfortable with cold water? (Bodies often "hit bottom", and that means below ALL the thermoclines.
3) I assume you are not squeamish. That means you are not going to have difficulties handling human flesh that has the same appearance and qualities of saturated plumber's putty.
4) Are you ready for solo diving? Certainly, SAR is done in teams. However, in most search environments (lakes and floodwaters, to name a couple) you will be called upon to act independently, since visual contact with your team mates will usually be impossible.
I don't mean to be gross, but there are a lot of factors you need to consider before entering this type of activity. It's an extremely challenging venue and one that requires a great deal of experience and training. It is far removed from "normal" diving and demands a great deal of preparation and equipment to be done properly.
And then there are the psychological implications, but that is another entry.
If you get the required training, expertise, equipment, and experience and you still feel the call to volunteer, my prayers are with you...first,that the need for you to practice those skills will never arise and, second, that if you are called upon to render such services that you will be kept safe and that your search will be successful.
