SUP Balance Training - extreme alternatives

I SUP for fun... and mix in SUP related moves as a fun training alternative at the gym. Nothing beats being on the water, but these moves do make me feel more prepared/confident/conditioned to deal with various SUP conditions. I'm a fan of core-balance-stabilization training anyway, so this appeals to me. Calling this extreme is probably an insult to extreme athletes everywhere... I call it that to differentiate from normal (safer) GYM training and to make it clear that it's not recommended for all.. just sharing some possibilities and the idea that you can use your imagination to create sport specific exercise alternatives. As with most exercises, there are common sense progressions that work for different levels. note: I've read good things about other balance trainers and SUP simulators... but haven't had the pleasure of testing them out... I'm sure they'd be fun to train on... In the meantime, most gyms have at least some good ways to create balance challenges (and having a skateboard deck in y