I am no swim expert by any means, but I get a weekly newsletter to a sports performance email/club that talked about 'gym exercises' to help with strength for swimming.
The exercise that they mentioned was to use a high pulley machine and a handle for one hand - to mean not a lat pull down style handle... just a handle for one hand.
Then, go to your knees and put one hand in the handle. Now simulate the pulling motion, for example - freestyle, where your elbow is slightly bent, and then 'pull' like you would if you were in the water... do some sets for each hand, and therefore each arm. I finish this exercise with the handle and my hand around my waist and thigh area.
I've been doing that to help my shoulder strength - for a swimming motion, and I can also feel it in the 'pulling' motion that I get when I'm swimming.
Food for thought.