These are really good guys way better than expected, all of this footage underwater was on the lowest power . There are three power settings the top one will give a burn time of 30 mins , middle setting 2.5 hrs and the low setting over 7 hours . To give you some idea the high setting will easily light the big chamber at Minllyn and the large ones in Cwmorthin. We use them both underwater and also above, they do get a bit warm if run to long above the water . £55 each and cover my 15mm wide angle lens easy !