My favorite swim exercise is, we would call it the Christmas tree, but basically the top would be like a 200 meter freestyle or whatever and then you just like form a Christmas tree shortening it each time until you got the bottom there just like sprints and then go back up to the 200 meter.
There's a few awesome exercises for swim. I think one of my favorites is you're kind of like in a plank position and you have a big yoga ball at your feet and you just go for as long as you can. I would say if you're starting out aim like 20 to 30 seconds, but if you're kind of more experienced you could go a minute or so and you just flutter kick on it. So you kick your feet really fast on it. You can also do a butterfly kick and that kind of strengthens your shoulders, your core, but also helps you to stay in line because if you kind of get off balance it can be easy to fall sideways off the ball. So it's good to have a good line, straight line for swimming. So that's a great exercise you can do to kind of train your body to be in the right position.