Duct tape (while the tanks & strobes are dry) or tank bungees (big enough to fit the tank, with just enough extra stretch for the strobes to be held tightly). I have placed the strobes in the middle of double tanks and duct taped them in place. Or put a flat tank bungee around one tank, and put the strobe on the side of that tank.
In both cases the strobe needs to be near the bottom of the tank to improve light coverage. Be careful as the diver can knock the strobe off on the roof when walking to the entrance, or underwater. I now prefer the bungee method as strobes bounce back or fall off instead of getting damaged. I use a secondary clip on the strobe mounting ball to a hip d-ring or other attachment point on the tank bands to stop them falling off completely. Bungee also means you can adjust the positioning during the dive by sliding the strobe to the back of the tank if needed.
The cable/sensor should run up between the tanks or between tank and wing where it won't get tangled. There are a few options for placing the sensor:
- on the corrugated hose for the wing inflator using either a small elastic or black electrical tape while dry
- tucked into mask or helmet strap once the diver is in the water
- taped to the side of the loop for rebreather divers
- in the shoulder D-ring, with the sensor looped through and taped back to the cable so it points forwards when the diver is swimming in normal trim
- held in the hand of the diver
- tucked/taped to the back of their goodman handle for primary light, or under the strap of their computer
There are advantages and disadvantages to all of these placements. The main objective is to keep the sensor out of the diver's way, and pointing forwards to the camera. Gear falling or floating in front of the sensor will stop the strobe going off.
Have fun with it! I look forward to seeing your shots.