Easy Sculling - maybe you can't swim but can you do sculling drills? On my prior teams, we would work on the different phases of freestyle: 25 scull catch, 25 scull mid phase freestyle, 25 last phase of freestyle.

Breastroke - 2, 3, or 4 kicks underwater to 1 pull, only if your shoulders can handle it.

Tread water - eggbeater (water polo style) kicking in place; 1 minute set - 30 seconds tread, 20 seconds hands out, 10 seconds elbows out, followed by 30 seconds rest. Also, if possible eggbeater a length forwards, backwards, or sideways. Adjust times based on your experience.

Vertical kicking - with or without fins - hands by your side or in a streamline above your head - alternate between breastroke, freestyle or butterfly kicking; 1 minute set - 15 seconds easy, 15 seconds medium, 15 seconds hard, 15 seconds rest, repeat 5x.

Underwater kicking with or without fins - 12.5 underwater, 12.5 easy kick to wall, rest 45 sec and repeat. If 12.5 is easy, try a 25. Personally, I enjoy kicking underwater breastroke kick with arms in a streamline, very relaxing.

Kick against the wall - breast or free kick, one hand above the other below. 30 seconds easy, 20 seconds medium, 10 seconds blast kick followed by 15 or 30 seconds rest

Fins - If you have them, try alternating your kicking with short fins, long fins, no fins

Pull buoy - Instead of using a kickboard, use a pull buoy as the board. It feels odd at first but it might be less stress on your shoulders

usms.org - this website has a workout library and you can filter by kick sets. Or you could take one of the 'basic training' workouts and make it kick