Kicking only workouts

Greetings, I'm looking for any input on workouts that involve only kicking. I'm recovering from some shoulder issues but want to stay in the water. I'm a 39 y/o Masters Swimmer in pretty good shape. I routinely do 3,500 - 4,500 yard workouts when healthy. I'd be using Zoomers for these workouts. Any ideas/workouts would be greatly appreciated! Thanks so much!