Swimming for 4 year olds?

My 3 1/2 yr old daughter loves water: the tub, the sink, the kiddie pool. I am considering swimming lessons at the local indoor pool. Has anyone else put their child of that age in lessons? Will she learn in a few months or will she require more sessions? I ask because she really wanted dance lessons and we paid a lot for them and she had a lot of problems taking direction and was a bit disruptive, although she enjoyed going into the big room and dancing, LOL....