An onomatopoeia for splashing or sloshing water — the sound or action of water moving vigorously, or washing/flowing with plenty of water.
子どもたちが川でざぶざぶ遊んでいる。
The children are splashing around in the river.
洗い桶に服を入れて、ざぶざぶ水で洗った。
I put the clothes in the washbasin and scrubbed them with lots of water.
波が岸にざぶざぶ打ち寄せる音が聞こえる。
You can hear the waves splashing onto the shore.