Can a free diver get the bends or only divers who use SCUBA gear?

Answer 1

The short answer is yes, but it takes many repetitive dives in a short period.

Your body always has nitrogen from the air you breathe dissolved in it, and the amount of nitrogen that is dissolved depends on the pressure on your body. That pressure comes from the weight of the atmosphere pressing on you when you're on the surface. As you descend in the water the weight of the water increases the pressure, and your body can then absorb more nitrogen (or any other gas you breathe) in proportion to the increased pressure. Double the pressure, and your body can absorb twice as much nitrogen. Of course your body can only absorb the nitrogen that is inhaled. When the pressure is reduced on ascent the extra gas will be lost. If the reduction in pressure is small enough or slow enough the gas will remain in solution and be carried to the lungs to be exhaled. If the reduction is too much or too fast the gas will come out of solution and form bubbles. All forms of decompression sickness, including the bends, are caused by those bubbles.

Since Scuba divers use tanks with a large amount of air (and therefore nitrogen, which accounts for 79% of the air), they can absorb large amounts of nitrogen if they dive deep enough or long enough. Because free divers only use a single breath per dive they can't absorb very much nitrogen on a single dive. However, a free diver may go very deep for several minutes, and may absorb a great deal of the nitrogen that is in that single breath. If the free diver makes many repetitive dives in a short period of time they will absorb nitrogen on each dive, and they may absorb more than they have lost between dives. It is therefore possible, though difficult and unlikely, for a free diver to get the bends. There have been known case of this happening to pearl divers.

The most serious form of barotrauma, a group of problems caused when air expands on ascent, is pulmonary barotrauma, which is caused by over-expansion of air in the lungs. A breath of air taken at the surface will decrease in size as pressure increases during descent, and will re-expand as pressure decreases on ascent. This is not a problem for free divers, because the air won't expand beyond the original lungfull of air they originally took. Since SCUBA divers breath compressed air at depth air in their lungs can expand to much more than a lungfull if they hold their breatth while ascending. The volume of a breath taken at 33 feet will double during ascent to the surface. If that air remains in the lungs while expanding it can result in many forms of very serious damage, thus it is very important that SCUBA divers never hold their breath.

Answer 2

No. Bends comes from a build-up of gasses. When you freedive you don't have enough air in your lungs with you for that to be a problem. You're not staying down long enough either.