Consider this: I was getting around forty miles to the gallon in my car before I added some roof rails to it. Now I get around thirty five miles to the gallon! Having the extra wind resistance is very costly in the extra fuel I need for my vehicle.
It is the same with scuba diving. If you have scuba gear sticking out and hanging off or diving gear that is not essential, you will expend a lot more energy simply swimming along than if you and your scuba diving equipment were more streamlined. It seems obvious yet it is very common for novices to allow their scuba gear to trail along or for more experienced divers to configure their diving kit in a way that adds significant drag to their profile.
The first thing to be considered is “…do I really need this extra bit of diving equipment?…” Do you need three torches, two reels, camera, goody bag, emergency flag, knife and two line cutters, slate and Spare Air for a leisurely sports dive around the bay? Yes, all emergency scuba diving equipment and spare items are essential and should be appropriate for the type of diving you are doing. But consider leaving your 100 watt lantern behind for a summer reef dive!
Assuming that all the equipment you are carrying is necessary, the next thing is to ensure that its configuration is comfortable for use and doesn’t create unnecessary resistance in the water. Having hoses crossing each other creates clutter around the diver and extra drag and so you should take some time to plan the feeds from back to front. Then the hoses and equipment needs to be secured properly to the body in the place where they are to hand when needed. The use of retractable bungees, clips and Velcro can make for a very neat diver who in turn will be more streamlined.
Inappropriate configuration can lead to loose scuba gear that might damage wildlife, or scuba diving equipment that is uncomfortable to wear and use and consequently potentially dangerous. And remember, dragging console mounted expensive scuba diving computers through a wreck will definitely shorten their life!