I'm approx 180cm tall, and approx 115kg. I dive in a two piece 7mm pinnacle wetsuit and use a Mares Rover BCD with either 12l ali or a 15l steel faber. When diving with the 12l Ali I carry about 14.5kg however if I use a steel 12l can usually get away with 12kg. 15l steel faber use same weighting as 12l steel 12kg. + in each case the weight of the bottle, BCD and any other equipment carried on the dive. On a good day I can get away with less weight still. I think it improves with skill level and confidence in the water as well as good observation of other divers and instructors, oh yeah and with fitness. Before doing courses with Jamie Obern (courses - advanced, rescue, wreck, DM, PPB, equipment) and Andy Connor (courses SRD & Nitrox) I dived with between 17 - 20kg. All weights above listed for seawater situations In the lake 10kg about right weighting with same gear. I'm happier with less weight, look forward to the day I can dive with as little as some of the other people posting here.
You know the speed of light. So what is the speed of dark?