Playing in or with water — activities like splashing, swimming, or playing at the beach, pool, river, etc.
夏休みに海で子どもと水遊びをした。
I played in the water with my children at the beach during summer vacation.
暑い日は庭でバケツを使って水遊びをする。
On hot days, we play with water in the garden using a bucket.
小さな子は浅いプールでの水遊びが大好きだ。
Small children love playing in the shallow pool.