17 days and have gained .6 pounds

Could I be retaining water due to these exercises?

It is possible. New or changes to routines often lead to temporary weight gain.

My clothes (skirts) seem to fit a bit better.

This is a good sign that you are on the right track. Taking measurements and progress pictures can be great alternatives to the scale. The scale can be tricky and fickle.

It's been 17 days, I have weighed and logged everything faithfully, and have gained .6 pounds. I am under my net calorie goal for 16 days by about 200 calories

It looks like you want to lose 5 lbs according to your profile, so you should be running a pretty small deficit. Slow losses are easy to mask with water weight (as already mentioned with the exercise or if you just eat more sodium or carbs the day before you weigh in or many other reasons). I think it might be a little to early for you to start worrying.

Make sure you are logging as accurately as you can, small deficits are easy to erase if you are not careful.

http://community.myfitnesspal.com/en/discussion/1234699/logging-accurately-step-by-step-guide#latest

For now I would recommend just continuing with your current plan. If you don't start seeing the results you want in a few weeks then it might be time to adjust your calorie goal.

Sidenote: Looking at things from a different direction. What is driving you to lose the 5 lbs? If you want to just look a little toner or leaner another approach may be to eat at maintenance and recomp through exercise.

Water retention, due to a new exercise program is common. Keep doing what you're doing and it will come.