I've done cold water, warm water and salt water fly-fishing and I think there's a lot of difference. Being primarily a warm water fisherman because of geography, I gotta tell you that for me, the learning curve was pretty steep the first time I starting dead drifing nymph patterns for trout and again the first time I started sight casting for permit. I could never have gone from fishing for bluegill to bonefish without a great deal of study, and a significant purchase of new species-appropriate equipment.