Do you want to see the splash effect in the 1.18 trailer in the game? This Add-on adds a similar effect to the splash effect of the trailer! 
CAUTION: This add-on is incomplete and can stop working if too many mobs fall into the water at the same time.

When you apply add-on and open the map, you have to enter /function start and wait for 1 to appear in the chat window. If 1 appears in the chat window, the setting is all done.

Caution: The /function start command should be used only once.

In order for the splash effect to appear, it must fall from about two blocks high toward the water.

(Splash effect)

This effect still works only for players, cows, and pigs, and bugs can occur in multi-play.

Reference video :