when you dredge in low to no visibility you have to use your other sense to be safe like feeling with your hands or most of all your hearing, so go down slow and listen to all the noise like the engine on your dredge so you can know where it is, so you can get back to it if you get in trouble and it is running so you know you got air and the sound of the nozzle so you know where it is so you don't put your hands or feet near it and get them suck in and you listen to the sound of the material going up the nozzle and hose so you will know if you are over feeding your nozzle and listen to the sound that the different size rocks and gravel make so you can tell how big the rocks are by the sound they make and how your nozzle feels every time a rock goes up it and you can hear and feel the rock going up the hose and in to your box and you can use your nozzle or hand to go around your hole to feel for rocks in the wall so you will know how big and where they all are so you can have a good mental picture of your work area and where every thing is and some times you can design your hole so it gets some current flow throw it to help clear it out maybe go up stream and put some rock in a line to change the current to you hole and be come. you should be paying attention to all the sounds and how every thing is feeling all the time when you are down so you can dredge in total darkness.

Are you dredging in a pond? I did that once, it silts out fast even if you are dumping your tailings elsewhere.

KNOW YOUR OBSTRUCTIONS, bottom and floating vegetation, rock overhangs and HAVE A TENDER if you plan to SCUBA dredge. If in water shallower than 5', feel around and KNOW YOUR OBSTRUCTIONS!

Those and the bends are the two biggest injurers of bottom dwellers, as long as the air supply inlet is upwind and away from any combustion sources/exhausts.

Take care, be safe and come home with color!

Jeff,
  That's all good Thanks.

Nicholas,

  It's more or less a pond,  There is a very wide spot in the creek that has no significant waterflow to speak of.  I expect NO visibility during this dive.  It won't be my first in these conditions or worse, but would be the first towing a dredge.

Brad,

  I'm not sure of the exact depth but Bends shouldn't be a problem.  The water isn't more than 20ft (adjusted for Altitude).  I don't have an air pump on my dredge (thus the Scuba aspect) so I hadn't thought of the exhaust, but my Buddy does have an Air pump.  Thanks!

Chip,

Keeping your depth to less than 20', you should be good (double check the dive tables) for hours of bottom time.

Keep your intake upwind of any exhaust sources. CO (carbon monoxide) toxicity can be cumulative.