Hey! So the bends is caused when your body absorbs nitrogen during extended bottom time at depth when diving on SCUBA. This nitrogen is in gas form and expands as you ascend. It can become "stuck" in various parts of your body often in the joints. The term "Bends" comes from the fact that divers suffering at the surface would relieve the pain by bending their joints, hence becoming known as the bends. The time limits imposed on SCUBA divers at certain depths is specifically for avoiding absorbing too much nitrogen. The short amount of time that a recreational free-diver spends underwater will not cause excess nitrogen absorption. Slow ascent is required on SCUBA but not while free-diving. I could go in to a lot more detail about this topic but my answer would end up longer than the post!