I have also done a lot of river spearfihing and it can get quite hair-raising at times especially in dirty water in a area with Zambezi Sharks.
All rivers I speared in had a very strong current and I can give you the following advice..( I wont say that's the only way to do it, but it tends to work for me)
1) Use a cammo or black suit...mask fins and gloves because bright colours do not work in the river and the fish usually see you long before you see them.
2) Use a shorter reef gun, because you cannot move a long gun quickly enough in a river and the current tends to make the rubbers vibrate scaring the fish.
3)Keep your gun tucked under you only extending it for the shot...and try to extend it in a controlled flowing movement. Your shot must follow immediately.
5)Try to keep your buoy-line as short as possible...if there is too much line trailing behind you in a strong current and it get stuck on the bottom after you surfaced it will pull you under because of the current. I always use a buoyto avoid a possible boating accident.
6) I found it easiest to go down, find myself a good spot and face upstream lying completely motionless on the bottom. (Holding on too a rock so I do net get washed away)
Thats basically it...happy hunting
Ps I do not recommend river hunting for legal reasons...but it is great fun
