I'd suspect the bulb, as it's been ON for so long. That would explain a lot.

The bad part of what you described is that the airbag control unit was under water. Insurance should've covered that as part of the flood claim (if you made one).

To repair the airbag system, you might have to replace the control unit. They're available used and they are plentiful since they don't fail that often. The first course of action would be to check and see if the bulb works. If so, read the 700/900 FAQ and read out the airbag code to see what the problem is. I suspect the computer, not the airbag itself--especially if it never went under water. Also, the connections in the SRS system could be part of the problem.
--
Chris Herbst
1992 745, 68k

And others:
93 944, 150k
90 245, 110k
88 744, 160k
87 245, 185k