I was a competitive swimmer for over a decade. Swimming is an excellent workout for everyone. Almost zero impact, works your entire body and great for your heart. I enjoy getting in the pool for thirty minutes after lifting to gives all my muscles a little work. Consistent swimming will give you a strong "core," abs, back, chest and thighs.
That is great you do butterfly(most difficult of the four strokes). I also see you do some work with the pull bouy. I would suggest mixing in using the kick board so you get both isolating your upper and lower body. It looks like you have a great fitness workout though! good luck