most people don't understand that the concept of the torch is the extreme output under the limitation of portability and battery capacity. Water resistance should be similar to an off the shelf maglite at best. [would you use a maglite as your primary dive light? no? didn't think so]
Second, a Osram 64623 is an 12V 100W lamp, overdriven.
Unless you have something like a huge SLA attached to it, don't expect any amount of runtime on it. Its bright yes, but far from practical.
VCW said:
Will this light be possible to use underwater?
Where can I get the bulbs for this light?
How bout the batteries?
And are there any other bulbs that can have more battery runtime?
What material is the reflector?
Is it possible to switch it with something else?
No
http://www.bulbconnection.com/ViewItem/bcrw/itmid/132/oc/64623 HLX/item.html
Custom battery packs are available via PM to LuxLuthor
IIRC Osram 64440 may be an idea selection if your going for less output for more runtime, its a 12V 50W lamp with relatively identical size to the 64623
the reflector is most likely aluminum, with an orange peel texture to it.
there are 6 types of reflectors that are used in these "hotwires" each of them having cam or camless [focusing ability] choices. Low orange peel [LOP], Medium orange peel [MOP], Heavy Orange peel [HOP], Low stipple, Medium stipple, heavy stipple. the more texture yields a more even and softer beam, at the cost of throw.
The availability of cammed reflectors is indefinite, as these are custom components made by scratch by members here on the forum.
Places I know for reflectors
http://kaidomain.com/
PM Fivemega
PM Litho123
AFAIK THE TORCH uses a camless LOP
Assuming that the structural components still retain the maglite features it is possible to mod it into something else. Whatever you decide to mod it into please document it and take pics