I made this compact video light for underwater photography using my Sony FDR-X3000R underwater camera. It was just a week or two before my planned night dive, so I made a very quick design & implementation. It uses two 10W 12V COB LEDs, a boost regulator, a reed switch for power on/off by a magnetic slider. The rechargeable batteries are two Lithium-Ion 18650 type cells. I use 3400 mAh ORB-186P34 cells.
The results were suprisingly good. The light was even and powerful enough. I never ran out of battery. I placed a trimmer inside the battery cover that allowed adjustment of intensity. I do not run at max LED rated power, to increase battery operation time and to increase LED lifetime. The electronics and LEDs are waterproofed separately so if battery cover is leaking, only the batteries will be flooded.
Watch my YouTube video with the video light in action!