Sculling. It sounds like an archaeological term, like looking for skeleton heads, but it's not. In scuba diving, sculling is hand paddling, and there's no reason to do it and lots of reasons not to. Sculling requires energy, which means you're using extra air. Ultimately, that means a shorter dive. You'll also be tiring instead of relaxing, and with all that fluttering going on you'll probably never get a fish to swim within 10 yards of you. As Open Water students, we're all taught to swim with our fins, not with our arms. So why can you always find someone sculling? Weight problems: No, this isn?t about desserts. Using the wrong amount of lead is the main reason divers have poor buoyancy control, and poor buoyancy is the main reason divers scull. Too much lead often causes divers to use their arms to stay off the bottom. Weight placement, called trim, if done improperly can also cause sculling. Trim lesson No. 1: All the weight doesn't have to go on the belt. For example, I have a Zeagle weight-integrated BC and usually split my lead between the BC and a belt. The BC weight pockets are in the front above my waist. I wear the belt low with the weight on my back. This distributes the total weight over a larger area. There are many ways to manage trim. The simplest and cheapest way is to arrange the weights symmetrically on the belt and use retaining clips to keep them in place. Check your belt periodically to make sure it hasn't slipped down or rotated around your waist. Occasionally, the problem is too little weight. Remember, aluminum tanks become positively buoyant as you use air. If you start the dive neutrally buoyant instead of slightly negative, you'll probably spend the last 15 minutes of the dive arm-swimming just to stay down.The best method to avoid weighting problems is to keep an accurate logbook, noting lead quantity, wetsuit thickness, tank type and even your body weight. Refer to this information on future dives.Anxiety: Many divers scull because they're uncomfortable moving in three dimensions. I think instructors also unwittingly add anxiety with fearsome warnings about staying off reefs and coral. While important, the warnings need not be threatening. Habit: Sometimes sculling is a habit carried over from swimming. Or, it may just be something no instructor bothered to correct.Once your weighting and buoyancy are right, put your hands at your sides. If you still can't stop, fold your arms across your chest or hook your thumbs inside your weight belt like a cowboy with a holster. Or, hold your gauge console with both hands. Regardless of the cause, no one needs to scull.Brian Courtney is Sport Diver's senior editor and a PADI instructor.