There is always the possibility that they are just hiding from you untill they get used to their surroundings.
Are there any other fish in the pond that might be harrassing them? Also where did you get them? A lot of stores sell comets as feeders and they don't always come frome a good stock and may be sickly. Do they show any signs of illness or injury? Did you condition them to their new surroundings or just dump them in?
I would check your water temp as low temps can lead to sluggish fish. Also, is it oxygenated well? If your chemical ratios, temps, and all check out I wouldn't be too worried. They will probably come out soon.