For me it’s - off season training: strength, cardio, and mobility/stretching. This helps offset the abuse from the asymmetrical loading incurred from waterskiing.
then in season, warm up before skiing, stretch/mobility after. Give yourself rest days and mix in a few non skiing workouts.
Big fan of Jenny LaBaw’s program, I have worked with her directly and highly recommend it direct or via flow point method.
as I have gotten older, skipping post workout stretching/mobility exercises gets me in the most trouble. It makes a big difference in how sore I am the next day.