Dont do it. I am an experienced swimmer, water polo player, and triathlete.
Doing it is the same thing as trying to do yoga while lifting weights. Its hard enough contorting your body in those positions let alone adding resistance.
If you’re interested in swimming workouts do eggbeaters, try to tread water with your shoulders out of water.
Or tread with bricks in your hand. The entire point is being able to safely “bale” from whatever you are doing. If you get too tired with weight in the pool it can get very dangerous very fast.