when water from the Niagara system splashes on the wall, Wet effect is Possible

[ClockworkOcean]

This isn’t really Niagara, it’s a fluid sim.

The engine does have a fluid sim plugin

Unreal Engine 5.3 Real-Time Water Simulation with Splash & Foam - Niagara Fluids | RedefineFX

but you might be better off modelling it in Blender first, then moving it to the engine

Fluid Simulations for Beginners 💦 (Blender Tutorial)