Does carrying extra weight reduce the amount of backwards and forwards movement from surge? Or just help you stick to the bottom to anchor yourself (when that's appropriate to do)?
The weight is only so you can get very negative on the bottom....like more than 10 pounds negative.....enough so that the surge or current will not move you around, and so that you can hold your camera dead still....again, to do this you have to find places where your lying on the bottom will not destroy marine life--you can NOT do this on top of a delicate coral reef....you can do it on blank sand just next to a patch reef with macro life you can shoot by being adjacent to it.
Muck diving it is much more troublesome than sand, because there is alot of life, even in the silty bottom that looks just like a mud bottom....
There are skilled photographers that care more about their shots than the marine life, that often do damage to a muck bottom---and there are good shooters that are very careful, and most likely do not damage the bottom at all.....And when you see the ones that tend to silt the heck out of the area each time they lie down, or ascend up to go to the next spot--figure they are causing plenty of damage with the poor control they are exercising...
If you are silting, you are showing poor control --which indicates you may not have the skill to be this close to a delicate bottom. If you are lying on the bottom, and heavy, you don't just swim up....you have to inflate your BC, being ascending to the point your fins are well off the bottom, and then get neutral and begin frog kicking if you are still any where near the bottom.....and you really need perfect trim--flat horizontal, so your feet are not down with head up, and this has you roto-tilling the bottom.
Here is a video of my friend Errol K demonstrating the proper trim and kicking techniques for a diver shooting macro in a silty and delicate environment. It does not show surge... or lying on the bottom, as his camera has a 60 MM lens so he can actually hover with it ( magnification is not huge as with a 100 or with an added diopter).
If Errol had to lie on the bottom for surge, the touch down would be gentile, in an area he felt he would not damage, and when he was done, he would ascend flat horizontal, with ZERO SILTING..to the point of regaining enough height off the bottom to begin frog kicking again..
[video=youtube_share;kWrlXJ_EL_k]http://youtu.be/kWrlXJ_EL_k[/video]