I went kayaking and had trouble holding my breath.

'It's not a breathing problem," says Jim Sausville, a kayaking instructor for USA Kayaking. "It's an anxiety problem." He notes that many of his students get so freaked out at the possibility of being upside down in the water that they literally forget to breathe. The solution to the physical side of the problem is simple: "As you're flipping over you need to relax and take a nice deep breath. The fear of flipping is shutting down your breathing." And no, you don't have to have the lung capacity of a skin diver to do a simple Eskimo roll or a wet exit. Sausville notes that a healthy human can hold his or her breath for 30 seconds with no problem. By comparison, it takes about three seconds to right a kayak. In short, you don't need bigger lungs, just a little more confidence. Simply practice in-water moves in a safe, nonthreatening environment. "Go to a pool or a warm, calm body of water with a friend you trust." Sausville suggests. (A friend who also happens to be an experienced kayaker will do nicely.)
First, he recommends practicing the wet exit both with and without a spray skirt. But don't make a beeline for the surface. "You have to get comfortable underwater," says Sausville. Instead try tapping the bottom of the kayak five times before coming up for air. This will add only a few seconds to the process, but it will reduce the panic factor significantly. Then Sausville suggests enlisting your friend to practice the T-rescue, for those times when you find yourself upside down in the river without the proverbial paddle. First you should reach up and signal for help. That's your partner's cue to move his or her kayak to the bow of your boat to help stabilize it. You then grab the bow of the other boat, pull your head above water, and then right your boat with your hips. Again, this whole maneuver should take less time than it did to read this paragraph.