Round pool lilos would be nice.
https://image.freepik.com/free-photo/family-swimming-pool-aerial-view-from-happy-mother-kids-swim-inflatable-ring-donuts-have-fun-water-family-vacation-tropical-holidays-resort_146539-1570.jpg
and swimming class for babies or toddlers.
https://c8.alamy.com/comp/P179TA/happy-family-mother-father-baby-son-learn-to-swim-training-to-dive-underwater-with-fun-in-swimming-pool-healthy-lifestyle-active-parents-P179TA.jpg
Would be nice if they brought backs some of the pool games from TS2. They used to dive under water and play Marco Polo. Pool parties would be lovely and the community pool should attract adult sims also, not just kids.