On Tuesday, August 19, 2003 8:43 AM, Kenneth Smith wrote:

> this is a good question that came up on Shark-L.
> I have felt the compression effects from dynamite fishing while in close
> proximity, but would like to hear others.

(snipped)

The blast characteristics will be determined by the type and quantity of
explosive and the tamping effect of depth, (pressure).  The explosion will
produce a shock wave that'll be transmitted through the water (just like
wave action on the surface) but the actual "work" of the explosion will be
done by a rapidly expanding bubble of heated gas that will continue to
expand; cool; collapse; heat up; expand; cool; collapse, etc. until its
energy is expended.

While there's no real "safe" distance from a detonation, there's a formula
for working out "safe" and "lethal" distances where the type and quantity of
explosives are known - and I don't think that it's neccessary to put that
formula here!

As a denser medium than air, the concussive effect of an underwater blast
can be more pronounced than on the surface and cause considerable damage to
the soft tissues and organs of the body.  Anybody who's been, for example,
in the vicinity when a "fish bomb" has been detonated some distance away
will feel their lungs suddenly compressed.  Shock waves travel faster than
sound waves.

The sound waves and the shock waves will both be generated by that series of
rapidly expanding and collapsing gas bubbles rising to the surface, so -
assuming that you weren't in the immediate vicinity of the blast and
depending on its depth - being deeper *might* be better???

Strike