what's the best way to work & see underwater at 45m where there is zero visibility due to mud & silt?

Answer 1

Commercial divers often have to work by feel. Generally "plan your dive, dive your plan" is a good idea, before the dive decide with your buddy and dive master exactly what you plan to accomplish. It's not an easy job. Sometimes they have to dive in sewers!

Answer 2

Well, at that depth, I can assume you aren't doing a hull survey, and with that kind of turbidity, you aren't in the tropics looking for aquarium fish, and if you were a rigger, you would already know this, so my guess is you are stealing portholes illegally off of great lakes wrecks.
In that case, its important to tie off the porthole first, so you don't lose it. Then, work off the light of the broco. Of course, you won't be able to see the flame, but keep steady pressure as the rod is consumed, you can feel it going down. If the glow turns from blue to orange, you aren't cutting, you're just wasting rod and O2.
without further details, this is as much as I can say.

Answer 3

Listen, I'm not a Geology teacher.