soaked or drenched (with water); sopping; slushy — describing something thoroughly wet
雨に降られて服がビシャビシャになった。
I got caught in the rain and my clothes are soaked.
子どもが水たまりで遊んで靴がビシャビシャだ。
The child played in the puddles and their shoes are sopping wet.
濡れた新聞紙を床に置いたら、ビシャビシャになってしまった。
When I put the wet newspaper on the floor, it became soaked.
splashing or sloshing (with a sound); used adverbially to describe splashing movements or noises
子どもたちは長靴で水たまりをビシャビシャと踏んで遊んでいる。
The children are stomping on puddles with their boots, splashing around.
犬が川に飛び込んでビシャビシャと水しぶきをあげた。
The dog jumped into the river and splashed the water everywhere.
窓を拭かずに雑巾を押すと、汚れがビシャビシャと広がった。
If you press the rag without wiping the window, the dirt spreads with a splashing motion.