Which could one say?

1. The thing I hate the most is when you go into the shower and you turn it on. At first the water is really cold and when the water hits the ground it splatters you/splashes you.

2 .... the shower splashes/splatters you with cold water at first.

Which would you use?

Hard to say; it depends on the shower head and the water pressure. 'Splashing' requires more liquid than 'splattering'.
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OK thank you,

but would it be

Water splattered/splashed me


the shower splattered/splashed me with water.

Both are fine.